27 Managing Resources with Oracle Database Resource Manager
Oracle Database Resource Manager (Resource Manager) enables you to manage resource allocation for a database.
Note:
This chapter discusses using PL/SQL package procedures to administer the Resource Manager. An easier way to administer the Resource Manager is with the graphical user interface of Oracle Enterprise Manager Cloud Control (Cloud Control). For instructions about administering Resource Manager with Cloud Control, see the Cloud Control online help.
To use Resource Manager with Cloud Control:
-
Access the Database Home Page.
-
From the Administration menu, select Resource Manager.
- About Oracle Database Resource Manager
Oracle Database Resource Manager (the Resource Manager) enables you to manage multiple workloads within a database that are contending for system and database resources. - Assigning Sessions to Resource Consumer Groups
There are automatic and manual methods that database administrators, users, and applications can use to assign sessions to resource consumer groups. When a session is assigned to a resource consumer group, Oracle Database Resource Manager (the Resource Manager) can manage resource allocation for it. - The Types of Resources Managed by the Resource Manager
Resource plan directives specify how resources are allocated to resource consumer groups or subplans. Each directive can specify several different methods for allocating resources to its consumer group or subplan. - Creating a Simple Resource Plan
You can quickly create a simple resource plan that is adequate for many situations using theCREATE_SIMPLE_PLAN
procedure. - Creating a Complex Resource Plan
When your situation calls for a more complex resource plan, you must create the plan, with its directives and consumer groups, in a staging area called the pending area, and then validate the plan before storing it in the data dictionary. - Enabling Oracle Database Resource Manager and Switching Plans
You enable Oracle Database Resource Manager (the Resource Manager) by setting theRESOURCE_MANAGER_PLAN
initialization parameter. This parameter specifies the top plan, identifying the plan to be used for the current instance. If no plan is specified with this parameter, the Resource Manager is not enabled. - Putting It All Together: Oracle Database Resource Manager Examples
Examples illustrate how to allocate resources with Resource Manager. - Managing Multiple Database Instances on a Single Server
Oracle Database provides a method for managing CPU allocations on a multi-CPU server running multiple database instances. This method is called instance caging. Instance caging and Oracle Database Resource Manager (the Resource Manager) work together to support desired levels of service across multiple instances. - Maintaining Consumer Groups, Plans, and Directives
You can maintain consumer groups, resource plans, and resource plan directives for Oracle Database Resource Manager (the Resource Manager). You perform maintenance tasks using theDBMS_RESOURCE_MANAGER
PL/SQL package. - Viewing Database Resource Manager Configuration and Status
You can use several static data dictionary views and dynamic performance views to view the current configuration and status of Oracle Database Resource Manager (the Resource Manager). - Monitoring Oracle Database Resource Manager
A set of dynamic performance views enable you to monitor the results of your Oracle Database Resource Manager settings. - Interacting with Operating-System Resource Control
Many operating systems provide tools for resource management. These tools often contain "workload manager" or "resource manager" in their names, and are intended to allow multiple applications to share the resources of a single server, using an administrator-defined policy. Examples are Hewlett Packard's Process Resource Manager or Solaris Containers, Zones, and Resource Pools. - Oracle Database Resource Manager Reference
Resource Manager includes predefined resource plans, consumer groups, and consumer groups mapping rules. You can query data dictionary views for information about your Resource Manager configuration.
Parent topic: Database Resource Management and Task Scheduling
27.1 About Oracle Database Resource Manager
Oracle Database Resource Manager (the Resource Manager) enables you to manage multiple workloads within a database that are contending for system and database resources.
- What Solutions Does the Resource Manager Provide for Workload Management?
Resource Manager allows the database to have more control over how hardware resources are allocated. - The Elements of Resource Manager
Resource Manager includes several elements that you can manage. - About Resource Manager Administration Privileges
You must have the required privileges to administer the Resource Manager.
Parent topic: Managing Resources with Oracle Database Resource Manager
27.1.1 What Solutions Does the Resource Manager Provide for Workload Management?
Resource Manager allows the database to have more control over how hardware resources are allocated.
When database resource allocation decisions are left to the operating system, you may encounter the following problems with workload management:
-
Excessive overhead
Excessive overhead results from operating system context switching between Oracle Database server processes when the number of server processes is high.
-
Inefficient scheduling
The operating system deschedules database servers while they hold latches, which is inefficient.
-
Inappropriate allocation of resources
The operating system distributes resources equally among all active processes and cannot prioritize one task over another.
-
Inability to manage database-specific resources, such as parallel execution servers and active sessions
The Resource Manager helps to overcome these problems by allowing the database more control over how hardware resources are allocated. In an environment with multiple concurrent user sessions that run jobs with differing priorities, all sessions should not be treated equally. The Resource Manager enables you to classify sessions into groups based on session attributes, and to then allocate resources to those groups in a way that optimizes hardware utilization for your application environment.
With the Resource Manager, you can:
-
Guarantee certain sessions a minimum amount of CPU regardless of the load on the system and the number of users.
-
Distribute available CPU by allocating percentages of CPU time to different users and applications. In a data warehouse, a higher percentage can be given to ROLAP (relational online analytical processing) applications than to batch jobs.
-
Limit the degree of parallelism of any operation performed by members of a group of users.
-
Manage the order of parallel statements in the parallel statement queue. Parallel statements from a critical application can be enqueued ahead of parallel statements from a low priority group of users.
-
Limit the number of parallel execution servers that a group of users can use. This ensures that all the available parallel execution servers are not allocated to only one group of users.
-
Create an active session pool. An active session pool consists of a specified maximum number of user sessions allowed to be concurrently active within a group of users. Additional sessions beyond the maximum are queued for execution, but you can specify a timeout period, after which queued jobs will terminate. The active session pool limits the total number of sessions actively competing for resources, thereby enabling active sessions to make faster progress.
-
Monitor resources
Automatically record statistics about resource usage. You can examine these statistics using real-time SQL monitoring and the Resource Manager dynamic performance views (the
V$RSRC_*
views). See "Monitoring Oracle Database Resource Manager" for information about using real-time SQL monitoring and the Resource Manager dynamic performance views. -
Limit the amount of PGA memory used by each session that belongs to a group of users.
-
Manage runaway sessions or calls in the following ways:
-
By detecting when a session or call consumes more than a specified amount of CPU, physical I/O, logical I/O, or elapsed time, and then automatically either terminating the session or call, or switching to a consumer group with a lower resource allocation or a limit on the percentage of CPU that the group can use. The SQL statements that are terminated due to their excessive consumption of system resources are quarantined, that is, they are not allowed to run again by generating compilation errors during their subsequent runs.
A logical I/O, also known as a buffer I/O, refers to reads and writes of buffers in the buffer cache. When a requested buffer is not found in memory, the database performs a physical I/O to copy the buffer from either disk or the flash cache into memory, and then a logical I/O to read the cached buffer.
-
By recording detailed information about SQL statements that consume more than a specified amount of CPU, physical I/O, logical I/O, or elapsed time with real-time SQL monitoring.
-
By using the Automatic Workload Repository (AWR) to analyze a persistent record of SQL statements that consume more than a specified amount of CPU, physical I/O, logical I/O, or elapsed time.
-
By logging information about a runaway session without taking any other action related to the session.
-
-
Prevent the execution of operations that the optimizer estimates will run for a longer time than a specified limit.
-
Limit the amount of time that a session can be idle. This can be further defined to mean only sessions that are blocking other sessions.
-
Allow a database to use different resource plans, based on changing workload requirements. You can dynamically change the resource plan, for example, from a daytime resource plan to a nighttime resource plan, without having to shut down and restart the instance. You can also schedule a resource plan change with Oracle Scheduler. See Oracle Scheduler Concepts for more information.
Parent topic: About Oracle Database Resource Manager
27.1.2 The Elements of Resource Manager
Resource Manager includes several elements that you can manage.
- About the Elements of Resource Manager
The elements of the Resource Manager include resource consumer groups, resource plans, and resource plan directives. - About Resource Consumer Groups
A resource consumer group (consumer group) is a collection of user sessions that are grouped together based on their processing needs. - About Resource Plan Directives
The Resource Manager allocates resources to consumer groups according to the set of resource plan directives (directives) that belong to the currently active resource plan. - About Resource Plans
A resource plan is a container for directives that specify how resources are allocated to resource consumer groups. - Example: A Simple Resource Plan
An example illustrates a simple resource plan. - About Subplans
Instead of referencing a consumer group, a resource plan directive (directive) can reference another resource plan. In this case, the plan is referred to as a subplan. - Example: A Resource Plan with Subplans
An example illustrates a resource plan with subplans.
Parent topic: About Oracle Database Resource Manager
27.1.2.1 About the Elements of Resource Manager
The elements of the Resource Manager include resource consumer groups, resource plans, and resource plan directives.
Element | Description |
---|---|
Resource consumer group |
A group of sessions that are grouped together based on resource requirements. The Resource Manager allocates resources to resource consumer groups, not to individual sessions. |
Resource plan |
A container for directives that specify how resources are allocated to resource consumer groups. You specify how the database allocates resources by activating a specific resource plan. |
Resource plan directive |
Associates a resource consumer group with a particular plan and specifies how resources are to be allocated to that resource consumer group. |
You use the DBMS_RESOURCE_MANAGER
PL/SQL package to create and maintain these elements. The elements are stored in tables in the data dictionary. You can view information about them with data dictionary views.
See Also:
Parent topic: The Elements of Resource Manager
27.1.2.2 About Resource Consumer Groups
A resource consumer group (consumer group) is a collection of user sessions that are grouped together based on their processing needs.
When a session is created, it is automatically mapped to a consumer group based on mapping rules that you set up. As a database administrator (DBA), you can manually switch a session to a different consumer group. Similarly, an application can run a PL/SQL package procedure that switches its session to a particular consumer group.
Because the Resource Manager allocates resources (such as CPU) only to consumer groups, when a session becomes a member of a consumer group, its resource allocation is determined by the allocation for the consumer group.
There are special consumer groups that are always present in the data dictionary. They cannot be modified or deleted. They are:
-
SYS_GROUP
This is the initial consumer group for all sessions created by user accounts
SYS
orSYSTEM
. This initial consumer group can be overridden by session-to-consumer group mapping rules. -
OTHER_GROUPS
This consumer group contains all sessions that have not been assigned to a consumer group. Every resource plan must contain a directive to
OTHER_GROUPS
.
There can be no more than 28 resource consumer groups in any active plan.
Parent topic: The Elements of Resource Manager
27.1.2.3 About Resource Plan Directives
The Resource Manager allocates resources to consumer groups according to the set of resource plan directives (directives) that belong to the currently active resource plan.
There is a parent-child relationship between a resource plan and its resource plan directives. Each directive references one consumer group, and no two directives for the currently active plan can reference the same consumer group.
A directive has several ways in which it can limit resource allocation for a consumer group. For example, it can control how much CPU the consumer group gets as a percentage of total CPU, and it can limit the total number of sessions that can be active in the consumer group. See "The Types of Resources Managed by the Resource Manager" for more information.
Parent topic: The Elements of Resource Manager
27.1.2.4 About Resource Plans
A resource plan is a container for directives that specify how resources are allocated to resource consumer groups.
In addition to the resource plans that are predefined for each Oracle database, you can create any number of resource plans. However, only one resource plan is active at a time. When a resource plan is active, each of its child resource plan directives controls resource allocation for a different consumer group. Each plan must include a directive that allocates resources to the consumer group named OTHER_GROUPS
. OTHER_GROUPS
applies to all sessions that belong to a consumer group that is not part of the currently active plan.
Note:
Although the term "resource plan" (or just "plan") denotes one element of the Resource Manager, in this chapter it is also used to refer to a complete resource plan schema, which includes the resource plan element itself, its resource plan directives, and the consumer groups that the directives reference. For example, when this chapter refers to the DAYTIME
resource plan, it could mean either the resource plan element named DAYTIME
, or the particular resource allocation schema that the DAYTIME
resource plan and its directives define. Thus, for brevity, it is acceptable to say, "the DAYTIME
plan favors interactive applications over batch applications."
Parent topic: The Elements of Resource Manager
27.1.2.5 Example: A Simple Resource Plan
An example illustrates a simple resource plan.
Figure 27-1 shows a simple resource plan for an organization that runs online transaction processing (OLTP) applications and reporting applications simultaneously during the daytime. The currently active plan, DAYTIME
, allocates CPU resources among three resource consumer groups. Specifically, OLTP
is allotted 75% of the CPU time, REPORTS
is allotted 15%, and OTHER_GROUPS
receives the remaining 10%. Any group can use more resources than it is guaranteed if there is no resource contention. For example, OLTP
is guaranteed 75% of the CPU, but if there is no resource contention, it can use up to 100% of the CPU.
Oracle Database provides a procedure (CREATE_SIMPLE_PLAN
) that enables you to quickly create a simple resource plan. This procedure is discussed in "Creating a Simple Resource Plan ".
Note:
The currently active resource plan does not enforce allocations until CPU usage is at 100%. If the CPU usage is below 100%, the database is not CPU-bound and hence there is no need to enforce allocations to ensure that all sessions get their designated resource allocation.
In addition, when allocations are enforced, unused allocation by any consumer group can be used by other consumer groups. In the previous example, if the OLTP
group does not use all of its allocation, the Resource Manager permits the REPORTS
group or OTHER_GROUPS
group to use the unused allocation.
Parent topic: The Elements of Resource Manager
27.1.2.6 About Subplans
Instead of referencing a consumer group, a resource plan directive (directive) can reference another resource plan. In this case, the plan is referred to as a subplan.
The subplan itself has directives that allocate resources to consumer groups and other subplans. The resource allocation scheme then works like this: The top resource plan (the currently active plan) divides resources among consumer groups and subplans. Each subplan allocates its portion of the total resource allocation among its consumer groups and subplans. You can create hierarchical plans with any number of subplans.
You create a resource subplan in the same way that you create a resource plan. To create a plan that is to be used only as a subplan, you use the SUB_PLAN
argument in the package procedure DBMS_RESOURCE_MANAGER.CREATE_PLAN
.
In any top level plan, you can reference a subplan only once. A subplan is not required to have a directive to OTHER_GROUPS
and cannot be set as a resource plan.
Parent topic: The Elements of Resource Manager
27.1.2.7 Example: A Resource Plan with Subplans
An example illustrates a resource plan with subplans.
In this example, the Great Bread Company allocates the CPU resource as shown in Figure 27-2. The figure illustrates a top plan (GREAT_BREAD
) and all of its descendents. For simplicity, the requirement to include the OTHER_GROUPS
consumer group is ignored, and resource plan directives are not shown, even though they are part of the plan. Rather, the CPU percentages that the directives allocate are shown along the connecting lines between plans, subplans, and consumer groups.
The GREAT_BREAD
plan allocates resources as follows:
-
20% of CPU resources to the consumer group
MARKET
-
60% of CPU resources to subplan
SALES_TEAM
, which in turn divides its share equally between theWHOLESALE
andRETAIL
consumer groups -
20% of CPU resources to subplan
DEVELOP_TEAM
, which in turn divides its resources equally between theBREAD
andMUFFIN
consumer groups
It is possible for a subplan or consumer group to have multiple parents. An example would be if the MARKET
group were included in the SALES_TEAM
subplan. However, a plan cannot contain any loops. For example, the SALES_TEAM
subplan cannot have a directive that references the GREAT_BREAD
plan.
See Also:
"Putting It All Together: Oracle Database Resource Manager Examples" for an example of a more complex resource plan.
Parent topic: The Elements of Resource Manager
27.1.3 About Resource Manager Administration Privileges
You must have the required privileges to administer the Resource Manager.
You must have the system privilege ADMINISTER_RESOURCE_MANAGER
to administer the Resource Manager. This privilege (with the ADMIN
option) is granted to database administrators through the DBA
role.
Being an administrator for the Resource Manager enables you to execute all of the procedures in the DBMS_RESOURCE_MANAGER
PL/SQL package.
You may, as an administrator with the ADMIN
option, choose to grant the administrative privilege to other users or roles. To do so, use the DBMS_RESOURCE_MANAGER_PRIVS
PL/SQL package. The relevant package procedures are listed in the following table.
Procedure | Description |
---|---|
|
Grants the |
|
Revokes the |
The following PL/SQL block grants the administrative privilege to user HR
, but does not grant HR
the ADMIN
option. Therefore, HR
can execute all of the procedures in the DBMS_RESOURCE_MANAGER
package, but HR
cannot use the GRANT_SYSTEM_PRIVILEGE
procedure to grant the administrative privilege to others.
BEGIN DBMS_RESOURCE_MANAGER_PRIVS.GRANT_SYSTEM_PRIVILEGE( GRANTEE_NAME => 'HR', PRIVILEGE_NAME => 'ADMINISTER_RESOURCE_MANAGER', ADMIN_OPTION => FALSE); END; /
You can revoke this privilege using the REVOKE_SYSTEM_PRVILEGE
procedure.
Note:
The ADMINISTER_RESOURCE_MANAGER
system privilege can only be granted or revoked using the DBMS_RESOURCE_MANAGER_PRIVS
package. It cannot be granted or revoked through the SQL GRANT
or REVOKE
statements.
See Also:
-
Oracle Database PL/SQL Packages and Types Reference. for information about the
DBMS_RESOURCE_MANAGER
package -
Oracle Database PL/SQL Packages and Types Reference. for information about the
DBMS_RESOURCE_MANAGER_PRIVS
package -
Oracle Database Security Guide for information about the
ADMIN
option
Parent topic: About Oracle Database Resource Manager
27.2 Assigning Sessions to Resource Consumer Groups
There are automatic and manual methods that database administrators, users, and applications can use to assign sessions to resource consumer groups. When a session is assigned to a resource consumer group, Oracle Database Resource Manager (the Resource Manager) can manage resource allocation for it.
Note:
Sessions that are not assigned to a consumer group are placed in the consumer group OTHER_GROUPS
.
- Overview of Assigning Sessions to Resource Consumer Groups
Before you enable the Resource Manager, you must specify how user sessions are assigned to resource consumer groups. - Assigning an Initial Resource Consumer Group
The initial consumer group of a session is determined by the mapping rules that you configure. - Specifying Session-to-Consumer Group Mapping Rules
You can create and prioritize session-to-consumer group mapping rules. - Switching Resource Consumer Groups
You can switch the resource consumer group of a session. - Specifying Automatic Consumer Group Switching
You can configure the Resource Manager to automatically switch a session to another consumer group when a certain condition is met. - Granting and Revoking the Switch Privilege
A user or application must have the switch privilege to switch a session to a specified resource consumer group.
Parent topic: Managing Resources with Oracle Database Resource Manager
27.2.1 Overview of Assigning Sessions to Resource Consumer Groups
Before you enable the Resource Manager, you must specify how user sessions are assigned to resource consumer groups.
You do this by creating mapping rules that enable the Resource Manager to automatically assign each session to a consumer group upon session startup, based upon session attributes. After a session is assigned to its initial consumer group and is running, you can call a procedure to manually switch the session to a different consumer group. You would typically do this if the session is using excessive resources and must be moved to a consumer group that is more limited in its resource allocation. You can also grant the switch privilege to users and to applications so that they can switch their sessions from one consumer group to another.
The database can also automatically switch a session from one consumer group to another (typically lower priority) consumer group when there are changes in session attributes or when a session exceeds designated resource consumption limits.
Parent topic: Assigning Sessions to Resource Consumer Groups
27.2.2 Assigning an Initial Resource Consumer Group
The initial consumer group of a session is determined by the mapping rules that you configure.
For information on how to configure mapping rules, see "Specifying Session-to-Consumer Group Mapping Rules".
Parent topic: Assigning Sessions to Resource Consumer Groups
27.2.3 Specifying Session-to-Consumer Group Mapping Rules
You can create and prioritize session-to-consumer group mapping rules.
- About Session-to-Consumer Group Mapping Rules
You can specify the initial consumer group for a session and dynamically switch the session to a different consumer group if the session attributes change. - Creating Consumer Group Mapping Rules
You use theSET_CONSUMER_GROUP_MAPPING
procedure to map a session attribute/value pair to a consumer group. - Modifying and Deleting Consumer Group Mapping Rules
To modify a consumer group mapping rule, run theSET_CONSUMER_GROUP_MAPPING
procedure against the desired attribute/value pair, specifying a new consumer group. - Creating Mapping Rule Priorities
To resolve conflicting mapping rules, you can establish a priority ordering of the session attributes from most important to least important.
Parent topic: Assigning Sessions to Resource Consumer Groups
27.2.3.1 About Session-to-Consumer Group Mapping Rules
You can specify the initial consumer group for a session and dynamically switch the session to a different consumer group if the session attributes change.
By creating session-to-consumer group mapping rules, you can:
-
Specify the initial consumer group for a session based on session attributes.
-
Enable the Resource Manager to dynamically switch a running session to another consumer group based on changing session attributes.
The mapping rules are based on session attributes such as the user name, the service that the session used to connect to the database, or the name of the client program.
To resolve conflicts among mapping rules, the Resource Manager orders the rules by priority. For example, suppose user SCOTT
connects to the database with the SALES
service. If one mapping rule states that user SCOTT
starts in the MED_PRIORITY
consumer group, and another states that sessions that connect with the SALES
service start in the HIGH_PRIORITY
consumer group, mapping rule priorities resolve this conflict.
There are two types of session attributes upon which mapping rules are based: login attributes and run-time attributes. The login attributes are meaningful only at session login time, when the Resource Manager determines the initial consumer group of the session. Run-time attributes apply any time during and after session login. You can reassign a logged in session to another consumer group by changing any of its run-time attributes.
You use the SET_CONSUMER_GROUP_MAPPING
and SET_CONSUMER_GROUP_MAPPING_PRI
procedures to configure the automatic assignment of sessions to consumer groups. You must use a pending area for these procedures. (You must create the pending area, run the procedures, optionally validate the pending area, and then submit the pending area. For examples of using the pending area, see "Creating a Complex Resource Plan".)
A session is automatically switched to a consumer group through mapping rules at distinct points in time:
-
When the session first logs in, the mapping rules are evaluated to determine the initial group of the session.
-
If a session attribute is dynamically changed to a new value (which is only possible for run-time attributes), then the mapping rules are reevaluated, and the session might be switched to another consumer group.
Predefined Consumer Group Mapping Rules
Each Oracle database comes with a set of predefined consumer group mapping rules:
-
As described in "About Resource Consumer Groups", all sessions created by user accounts
SYS
orSYSTEM
are initially mapped to theSYS_GROUP
consumer group. -
Sessions performing a data load with Data Pump or performing backup or copy operations with RMAN are automatically mapped to the predefined consumer groups designated in Table 27-7.
You can use the DBMS_RESOURCE_MANAGER
.SET_CONSUMER_GROUP_MAPPING
procedure to modify or delete any of these predefined mapping rules.
27.2.3.2 Creating Consumer Group Mapping Rules
You use the SET_CONSUMER_GROUP_MAPPING
procedure to map a session attribute/value pair to a consumer group.
The parameters for this procedure are the following:
Parameter | Description |
---|---|
|
The session attribute type, specified as a package constant |
|
The value of the attribute |
|
The consumer group to map to for this attribute/value pair |
ATTRIBUTE
can be one of the following:
Attribute | Type | Description |
---|---|---|
|
Login |
The Oracle Database user name |
|
Login |
The database service name used by the client to establish a connection |
|
Login |
The operating system user name of the client that is logging in |
|
Login |
The name of the client program used to log in to the server |
|
Login |
The name of the computer from which the client is making the connection |
|
Login |
The client identifier for the session The client identifier session attribute is set by the |
|
Run-time |
The module name in the currently running application as set by the |
|
Run-time |
A combination of the current module and the action being performed as set by either of the following procedures or their equivalent OCI attribute setting:
The attribute is specified as the module name followed by a period (.), followed by the action name ( |
|
Run-time |
A combination of service and module names in this form: |
|
Run-time |
A combination of service name, module name, and action name, in this form: |
|
Run-time |
An RMAN or Data Pump operation. Valid values are |
For example, the following PL/SQL block causes user SCOTT
to map to the DEV_GROUP
consumer group every time that he logs in:
BEGIN DBMS_RESOURCE_MANAGER.SET_CONSUMER_GROUP_MAPPING (DBMS_RESOURCE_MANAGER.ORACLE_USER, 'SCOTT', 'DEV_GROUP'); END; /
Again, you must create a pending area before running the SET_CONSUMER_GROUP_MAPPING
procedure.
You can use wildcards for the value of most attributes in the value
parameter in the SET_CONSUMER_GROUP_MAPPING
procedure. To specify values with wildcards, use the same semantics as the SQL LIKE
operator. Specifically, wildcards use the following semantics:
-
%
for a multicharacter wildcard -
_
for a single character wildcard -
\
to escape the wildcards
Wildcards can only be used if the attribute is one of the following:
-
CLIENT_OS_USER
-
CLIENT_PROGRAM
-
CLIENT_MACHINE
-
MODULE_NAME
-
MODULE_NAME_ACTION
-
SERVICE_MODULE
-
SERVICE_MODULE_ACTION
Parent topic: Specifying Session-to-Consumer Group Mapping Rules
27.2.3.3 Modifying and Deleting Consumer Group Mapping Rules
To modify a consumer group mapping rule, run the SET_CONSUMER_GROUP_MAPPING
procedure against the desired attribute/value pair, specifying a new consumer group.
To delete a rule, run the SET_CONSUMER_GROUP_MAPPING
procedure against the desired attribute/value pair and specify a NULL
consumer group.
Parent topic: Specifying Session-to-Consumer Group Mapping Rules
27.2.3.4 Creating Mapping Rule Priorities
To resolve conflicting mapping rules, you can establish a priority ordering of the session attributes from most important to least important.
You use the SET_CONSUMER_GROUP_MAPPING_PRI
procedure to set the priority of each attribute to a unique integer from 1 (most important) to 12 (least important). The following example illustrates this setting of priorities:
BEGIN DBMS_RESOURCE_MANAGER.SET_CONSUMER_GROUP_MAPPING_PRI( EXPLICIT => 1, SERVICE_MODULE_ACTION => 2, SERVICE_MODULE => 3, MODULE_NAME_ACTION => 4, MODULE_NAME => 5, SERVICE_NAME => 6, ORACLE_USER => 7, CLIENT_PROGRAM => 8, CLIENT_OS_USER => 9, CLIENT_MACHINE => 10, CLIENT_ID => 11); END; /
In this example, the priority of the database user name is set to 7 (less important), while the priority of the module name is set to 5 (more important).
Note:
SET_CONSUMER_GROUP_MAPPING_PRI
requires that you include the pseudo-attribute EXPLICIT
as an argument. It must be set to 1. It indicates that explicit consumer group switches have the highest priority. You explicitly switch consumer groups with these package procedures, which are described in detail in Oracle Database PL/SQL Packages and Types Reference:
-
DBMS_SESSION.SWITCH_CURRENT_CONSUMER_GROUP
-
DBMS_RESOURCE_MANAGER.SWITCH_CONSUMER_GROUP_FOR_SESS
-
DBMS_RESOURCE_MANAGER.SWITCH_CONSUMER_GROUP_FOR_USER
To illustrate how mapping rule priorities work, continuing with the previous example, assume that in addition to the mapping of user SCOTT
to the DEV_GROUP
consumer group, there is also a module name mapping rule as follows:
BEGIN DBMS_RESOURCE_MANAGER.SET_CONSUMER_GROUP_MAPPING (DBMS_RESOURCE_MANAGER.MODULE_NAME, 'EOD_REPORTS', 'LOW_PRIORITY'); END; /
Now if the application in user SCOTT
's session sets its module name to EOD_REPORTS
, the session is reassigned to the LOW_PRIORITY
consumer group, because module name mapping has a higher priority than database user mapping.
You can query the view DBA_RSRC_MAPPING_PRIORITY
to see the current priority ordering of session attributes.
See Also:
-
Oracle Database PL/SQL Packages and Types Reference for information about setting the module name with the
DBMS_APPLICATION_INFO.SET_MODULE
procedure
Parent topic: Specifying Session-to-Consumer Group Mapping Rules
27.2.4 Switching Resource Consumer Groups
You can switch the resource consumer group of a session.
- Manually Switching Resource Consumer Groups
You can change the resource consumer group of running sessions. - Enabling Users or Applications to Manually Switch Consumer Groups
You can grant a user the switch privilege so that he can switch his current consumer group using theSWITCH_CURRENT_CONSUMER_GROUP
procedure in theDBMS_SESSION
package.
Parent topic: Assigning Sessions to Resource Consumer Groups
27.2.4.1 Manually Switching Resource Consumer Groups
You can change the resource consumer group of running sessions.
- About Manually Switching Resource Consumer Groups
TheDBMS_RESOURCE_MANAGER
PL/SQL package provides two procedures that enable you to change the resource consumer group of running sessions. - Switching a Single Session
TheSWITCH_CONSUMER_GROUP_FOR_SESS
procedure causes the specified session to immediately be moved into the specified resource consumer group. In effect, this procedure can raise or lower priority of the session. - Switching All Sessions for a User
TheSWITCH_CONSUMER_GROUP_FOR_USER
procedure changes the resource consumer group for all sessions pertaining to the specified user name.
Parent topic: Switching Resource Consumer Groups
27.2.4.1.1 About Manually Switching Resource Consumer Groups
The DBMS_RESOURCE_MANAGER
PL/SQL package provides two procedures that enable you to change the resource consumer group of running sessions.
Both of these procedures can also change the consumer group of any parallel execution server sessions associated with the coordinator session. The changes made by these procedures pertain to current sessions only; they are not persistent. They also do not change the initial consumer groups for users.
Instead of terminating a session of a user who is using excessive CPU, you can change that user's consumer group to one that is allocated fewer resources.
Parent topic: Manually Switching Resource Consumer Groups
27.2.4.1.2 Switching a Single Session
The SWITCH_CONSUMER_GROUP_FOR_SESS
procedure causes the specified session to immediately be moved into the specified resource consumer group. In effect, this procedure can raise or lower priority of the session.
The following PL/SQL block switches a specific session to a new consumer group. The session identifier (SID
) is 17, the session serial number (SERIAL#
) is 12345, and the new consumer group is the HIGH_PRIORITY
consumer group.
BEGIN DBMS_RESOURCE_MANAGER.SWITCH_CONSUMER_GROUP_FOR_SESS ('17', '12345', 'HIGH_PRIORITY'); END; /
The SID
, session serial number, and current resource consumer group for a session are viewable using the V$SESSION
view.
See Also:
Oracle Database Reference for details about the V$SESSION
view.
Parent topic: Manually Switching Resource Consumer Groups
27.2.4.1.3 Switching All Sessions for a User
The SWITCH_CONSUMER_GROUP_FOR_USER
procedure changes the resource consumer group for all sessions pertaining to the specified user name.
The following PL/SQL block switches all sessions that belong to user HR
to the LOW_GROUP
consumer group:
BEGIN DBMS_RESOURCE_MANAGER.SWITCH_CONSUMER_GROUP_FOR_USER ('HR', 'LOW_GROUP'); END; /
Parent topic: Manually Switching Resource Consumer Groups
27.2.4.2 Enabling Users or Applications to Manually Switch Consumer Groups
You can grant a user the switch privilege so that he can switch his current consumer group using the SWITCH_CURRENT_CONSUMER_GROUP
procedure in the DBMS_SESSION
package.
A user can run this procedure from an interactive session, for example from SQL*Plus, or an application can call this procedure to switch its session, effectively dynamically changing its priority.
The SWITCH_CURRENT_CONSUMER_GROUP
procedure enables users to switch to only those consumer groups for which they have the switch privilege. If the caller is another procedure, then this procedure enables users to switch to a consumer group for which the owner of that procedure has switch privileges.
The parameters for this procedure are the following:
Parameter | Description |
---|---|
|
The consumer group to which the user is switching. |
|
Returns the name of the consumer group from which the user switched. Can be used to switch back later. |
|
Controls behavior if a switching error occurs. If If |
The following SQL*Plus session illustrates switching to a new consumer group. By printing the value of the output parameter old_group
, the example illustrates how the old consumer group name is saved.
SET serveroutput on DECLARE old_group varchar2(30); BEGIN DBMS_SESSION.SWITCH_CURRENT_CONSUMER_GROUP('BATCH_GROUP', old_group, FALSE); DBMS_OUTPUT.PUT_LINE('OLD GROUP = ' || old_group); END; /
The following line is output:
OLD GROUP = OLTP_GROUP
Note that the Resource Manager considers a switch to have taken place even if the SWITCH_CURRENT_CONSUMER_GROUP
procedure is called to switch the session to the consumer group that it is already in.
Note:
The Resource Manager also works in environments where a generic database user name is used to log on to an application. The DBMS_SESSION
package can be called to switch the consumer group assignment of a session at session startup, or as particular modules are called.
See Also:
-
Oracle Database PL/SQL Packages and Types Reference for additional examples and more information about the
DBMS_SESSION
package
Parent topic: Switching Resource Consumer Groups
27.2.5 Specifying Automatic Consumer Group Switching
You can configure the Resource Manager to automatically switch a session to another consumer group when a certain condition is met.
Automatic switching can occur when: a session attribute changes, causing a new mapping rule to take effect, or a session exceeds the CPU, physical I/O, or logical I/O resource consumption limits set by its consumer group, or it exceeds the elapsed time limit set by its consumer group.
- Specifying Automatic Switching with Mapping Rules
If a session attribute changes while the session is running, then the session-to-consumer group mapping rules are reevaluated. If a new rule takes effect, then the session might be moved to a different consumer group. - Specifying Automatic Switching by Setting Resource Limits
You can manage runaway sessions or calls that use CPU, physical I/O, or logical I/O resources beyond a specified limit. A runaway session is a SQL query, while a runaway call is a PL/SQL call.
Parent topic: Assigning Sessions to Resource Consumer Groups
27.2.5.1 Specifying Automatic Switching with Mapping Rules
If a session attribute changes while the session is running, then the session-to-consumer group mapping rules are reevaluated. If a new rule takes effect, then the session might be moved to a different consumer group.
See "Specifying Session-to-Consumer Group Mapping Rules" for more information.
Parent topic: Specifying Automatic Consumer Group Switching
27.2.5.2 Specifying Automatic Switching by Setting Resource Limits
You can manage runaway sessions or calls that use CPU, physical I/O, or logical I/O resources beyond a specified limit. A runaway session is a SQL query, while a runaway call is a PL/SQL call.
When you create a resource plan directive for a consumer group, you can specify limits for CPU, physical I/O, or logical I/O resource consumption for sessions in that group. You can specify limits for physical I/O and logical I/O separately. You can also specify a limit for elapsed time. If the SWITCH_FOR_CALL
resource plan directive is set to FALSE
, then Resource Manager enforces these limits from the start of the session. If the SWITCH_FOR_CALL
resource plan directive is set to TRUE
, then Resource Manager enforces these limits from the start of the SQL operation or PL/SQL block.
You can then specify the action that is to be taken if any single session or call exceeds one of these limits. The possible actions are the following:
-
The session is dynamically switched to a designated consumer group.
The target consumer group is typically one that has lower resource allocations.
-
The session is terminated.
-
The session's current SQL statement is terminated.
-
Information about the session is logged, but no other action is taken for the session.
The following are the resource plan directive attributes that are involved in this type of automatic session switching.
-
SWITCH_GROUP
-
SWITCH_TIME
-
SWITCH_ESTIMATE
-
SWITCH_IO_MEGABYTES
-
SWITCH_IO_REQS
-
SWITCH_FOR_CALL
-
SWITCH_IO_LOGICAL
-
SWITCH_ELAPSED_TIME
See "Creating Resource Plan Directives " for descriptions of these attributes.
Switches occur for sessions that are running and consuming resources, not waiting for user input or waiting for CPU cycles. After a session is switched, it continues in the target consumer group until it becomes idle, at which point it is switched back to its original consumer group. However, if SWITCH_FOR_CALL
is set to TRUE
, then the Resource Manager does not wait until the session is idle to return it to its original resource consumer group. Instead, the session is returned when the current top-level call completes. A top-level call in PL/SQL is an entire PL/SQL block treated as one call. A top-level call in SQL is an individual SQL statement.
SWITCH_FOR_CALL
is useful for three-tier applications where the middle tier server is using session pooling.
A switched session is allowed to continue running even if the active session pool for the new group is full. Under these conditions, a consumer group can have more sessions running than specified by its active session pool.
When SWITCH_FOR_CALL
is FALSE
, the Resource Manager views a session as idle if a certain amount of time passes between calls. This time interval is a few seconds and is not configurable.
The following are examples of automatic switching based on resource limits. You must create a pending area before running these examples.
Example 1
The following PL/SQL block creates a resource plan directive for the OLTP
group that switches any session in that group to the LOW_GROUP
consumer group if a call in the sessions exceeds 5 seconds of CPU time. This example prevents unexpectedly long queries from consuming too many resources. The switched-to consumer group is typically one with lower resource allocations.
BEGIN DBMS_RESOURCE_MANAGER.CREATE_PLAN_DIRECTIVE ( PLAN => 'DAYTIME', GROUP_OR_SUBPLAN => 'OLTP', COMMENT => 'OLTP group', MGMT_P1 => 75, SWITCH_GROUP => 'LOW_GROUP', SWITCH_TIME => 5); END; /
Example 2
The following PL/SQL block creates a resource plan directive for the OLTP
group that temporarily switches any session in that group to the LOW_GROUP
consumer group if the session exceeds 10,000 physical I/O requests or exceeds 2,500 Megabytes of data transferred. The session is returned to its original group after the offending top call is complete.
BEGIN DBMS_RESOURCE_MANAGER.CREATE_PLAN_DIRECTIVE ( PLAN => 'DAYTIME', GROUP_OR_SUBPLAN => 'OLTP', COMMENT => 'OLTP group', MGMT_P1 => 75, SWITCH_GROUP => 'LOW_GROUP', SWITCH_IO_REQS => 10000, SWITCH_IO_MEGABYTES => 2500, SWITCH_FOR_CALL => TRUE); END; /
Example 3
The following PL/SQL block creates a resource plan directive for the
REPORTING
group that terminates any session that exceeds 60 seconds of
CPU time. This example prevents runaway queries from consuming too many resources.
BEGIN DBMS_RESOURCE_MANAGER.CREATE_PLAN_DIRECTIVE ( PLAN => 'DAYTIME', GROUP_OR_SUBPLAN => 'REPORTING', COMMENT => 'Reporting group', MGMT_P1 => 75, SWITCH_GROUP => 'KILL_SESSION', SWITCH_TIME => 60); END; /
In this example, the reserved consumer group name KILL_SESSION
is specified for SWITCH_GROUP
. Therefore, the session is terminated when the switch criteria is met. Other reserved consumer group names are CANCEL_SQL
and LOG_ONLY
. When CANCEL_SQL
is specified, the current call is canceled when switch criteria are met, but the session is not terminated. When LOG_ONLY
is specified, information about the session is recorded in real-time SQL monitoring, but no specific action is taken for the session.
Example 4
The following PL/SQL block creates a resource plan directive for the OLTP
group that temporarily switches any session in that group to the LOW_GROUP
consumer group if the session exceeds 100 logical I/O requests. The session is returned to its original group after the offending top call is complete.
BEGIN DBMS_RESOURCE_MANAGER.CREATE_PLAN_DIRECTIVE ( PLAN => 'DAYTIME', GROUP_OR_SUBPLAN => 'OLTP', COMMENT => 'OLTP group', MGMT_P1 => 75, SWITCH_GROUP => 'LOW_GROUP', SWITCH_IO_LOGICAL => 100, SWITCH_FOR_CALL => TRUE); END; /
Example 5
The following PL/SQL block creates a resource plan directive for the OLTP
group that temporarily switches any session in that group to the LOW_GROUP
consumer group if a call in a session exceeds five minutes (300 seconds). The session is returned to its original group after the offending top call is complete.
BEGIN DBMS_RESOURCE_MANAGER.CREATE_PLAN_DIRECTIVE ( PLAN => 'DAYTIME', GROUP_OR_SUBPLAN => 'OLTP', COMMENT => 'OLTP group', MGMT_P1 => 75, SWITCH_GROUP => 'LOW_GROUP', SWITCH_FOR_CALL => TRUE, SWITCH_ELAPSED_TIME => 300); END; /
See Also:
-
"What Solutions Does the Resource Manager Provide for Workload Management?" for information about logical I/O
Parent topic: Specifying Automatic Consumer Group Switching
27.2.6 Granting and Revoking the Switch Privilege
A user or application must have the switch privilege to switch a session to a specified resource consumer group.
- About Granting and Revoking the Switch Privilege
Using theDBMS_RESOURCE_MANAGER_PRIVS
PL/SQL package, you can grant or revoke the switch privilege to a user, role, orPUBLIC
. The switch privilege enables a user or application to switch a session to a specified resource consumer group. - Granting the Switch Privilege
You can grant a user the privilege to switch to a specific consumer group using theGRANT_SWITCH_CONSUMER_GROUP
procedure. - Revoking Switch Privileges
You can revoke a user’s privilege to switch to a specific consumer group using theREVOKE_SWITCH_CONSUMER_GROUP
procedure.
Parent topic: Assigning Sessions to Resource Consumer Groups
27.2.6.1 About Granting and Revoking the Switch Privilege
Using the DBMS_RESOURCE_MANAGER_PRIVS
PL/SQL package, you can grant or revoke the switch privilege to a user, role, or PUBLIC
. The switch privilege enables a user or application to switch a session to a specified resource consumer group.
The package also enables you to revoke the switch privilege. The relevant package procedures are listed in the following table.
Procedure | Description |
---|---|
|
Grants permission to a user, role, or |
|
Revokes permission for a user, role, or |
OTHER_GROUPS
has switch privileges granted to PUBLIC
. Therefore, all users are automatically granted the switch privilege for this consumer group.
The following switches do not require explicit switch privilege:
-
There is a consumer group mapping specified by the
SET_CONSUMER_GROUP_MAPPING
procedure in theDBMS_RESOURCE_MANAGER
package, and a session is switching to a different consumer group due to the mapping. See "Creating Consumer Group Mapping Rules". -
There is an automatic consumer group switch when a switch condition is met based on the setting of the
switch_group
parameter of a resource plan directive.
Explicit switch privilege is required for a user to switch a session to a consumer group in all other cases.
27.2.6.2 Granting the Switch Privilege
You can grant a user the privilege to switch to a specific consumer group using the GRANT_SWITCH_CONSUMER_GROUP
procedure.
The following example grants user SCOTT
the privilege to switch to consumer group OLTP
.
BEGIN DBMS_RESOURCE_MANAGER_PRIVS.GRANT_SWITCH_CONSUMER_GROUP ( GRANTEE_NAME => 'SCOTT', CONSUMER_GROUP => 'OLTP', GRANT_OPTION => TRUE); END; /
User SCOTT
is also granted permission to grant switch privileges for OLTP
to others.
If you grant permission to a role to switch to a particular resource consumer group, then any user who is granted that role and has enabled that role can switch his session to that consumer group.
If you grant PUBLIC
the permission to switch to a particular consumer group, then any user can switch to that group.
If the GRANT_OPTION
argument is TRUE
, then users granted switch privilege for the consumer group can also grant switch privileges for that consumer group to others.
Parent topic: Granting and Revoking the Switch Privilege
27.2.6.3 Revoking Switch Privileges
You can revoke a user’s privilege to switch to a specific consumer group using the REVOKE_SWITCH_CONSUMER_GROUP
procedure.
The following example revokes user SCOTT
's privilege to switch to consumer group OLTP
.
BEGIN DBMS_RESOURCE_MANAGER_PRIVS.REVOKE_SWITCH_CONSUMER_GROUP ( REVOKEE_NAME => 'SCOTT', CONSUMER_GROUP => 'OLTP'); END; /
If you revoke a user's switch privileges for a particular consumer group, any subsequent attempts by that user to switch to that consumer group manually will fail. The user's session will then be automatically assigned to OTHER_GROUPS
.
If you revoke from a role the switch privileges to a consumer group, any users who had switch privileges for the consumer group only through that role are no longer able to switch to that consumer group.
If you revoke switch privileges to a consumer group from PUBLIC
, any users other than those who are explicitly assigned switch privileges either directly or through a role are no longer able to switch to that consumer group.
Parent topic: Granting and Revoking the Switch Privilege
27.3 The Types of Resources Managed by the Resource Manager
Resource plan directives specify how resources are allocated to resource consumer groups or subplans. Each directive can specify several different methods for allocating resources to its consumer group or subplan.
- CPU
To manage CPU resources, Resource Manager allocates resources among consumer groups and redistributes CPU resources that were allocated but were not used. You can also set a limit on the amount of CPU resources that can be allocated to a particular consumer group. - Exadata I/O
Management attributes enable you to specify CPU resource allocation for Exadata I/O. - Parallel Execution Servers
Resource Manager can manage usage of the available parallel execution servers for a database. - Program Global Area (PGA)
To manage PGA resources, Resource Manager can limit the amount of PGA memory that can be allocated to each session in a particular consumer group. - Runaway Queries
Runaway sessions and calls can adversely impact overall performance if they are not managed properly. Resource Manager can take action when a session or call consumes more than a specified amount of CPU, physical I/O, logical I/O, or elapsed time. Resource Manager can either switch the session or call to a consumer group that is allocated a small amount of CPU or terminate the session or call. - Active Session Pool with Queuing
You can control the maximum number of concurrently active sessions allowed within a consumer group. This maximum defines the active session pool. - Undo Pool
You can specify an undo pool for each consumer group. An undo pool controls the total amount of undo for uncommitted transactions that can be generated by a consumer group. - Idle Time Limit
You can specify an amount of time that a session can be idle, after which it is terminated.
Parent topic: Managing Resources with Oracle Database Resource Manager
27.3.1 CPU
To manage CPU resources, Resource Manager allocates resources among consumer groups and redistributes CPU resources that were allocated but were not used. You can also set a limit on the amount of CPU resources that can be allocated to a particular consumer group.
- Management Attributes
Management attributes enable you to specify how CPU resources are to be allocated among consumer groups and subplans. - Utilization Limit
Use theUTILIZATION_LIMIT
attribute to impose an absolute upper limit on CPU utilization for a resource consumer group. This absolute limit overrides any redistribution of CPU within a plan.
Parent topic: The Types of Resources Managed by the Resource Manager
27.3.1.1 Management Attributes
Management attributes enable you to specify how CPU resources are to be allocated among consumer groups and subplans.
Multiple levels of CPU resource allocation (up to eight levels) provide a means of prioritizing CPU usage within a plan. Consumer groups and subplans at level 2 get resources that were not allocated at level 1 or that were allocated at level 1 but were not completely consumed by a consumer group or subplan at level 1. Similarly, resource consumers at level 3 are allocated resources only when some allocation remains from levels 1 and 2. The same rules apply to levels 4 through 8. Multiple levels not only provide a way of prioritizing, but they provide a way of explicitly specifying how all primary and leftover resources are to be used.
Use the management attributes MGMT_P
n
, where n is an integer between 1 and 8, to specify multiple levels of CPU resource allocation. For example, use the MGMT_P1
directive attribute to specify CPU resource allocation at level 1 and MGMT_P2
directive attribute to specify resource allocation at level 2.
Use management attributes with parallel statement directive attributes, such as Degree of Parallelism Limit and Parallel Server Limit, to control parallel statement queuing. When parallel statement queuing is used, management attributes are used to determine which consumer group is allowed to issue the next parallel statement. For example, if you set the MGMT_P1
directive attribute for a consumer group to 80, that group has an 80% chance of issuing the next parallel statement.
See Also:
Oracle Database VLDB and Partitioning Guide for information about parallel statement queuing
Table 27-1 illustrates a simple resource plan with three levels.
Table 27-1 A Simple Three-Level Resource Plan
Consumer Group | Level 1 CPU Allocation | Level 2 CPU Allocation | Level 3 CPU Allocation |
---|---|---|---|
|
80% |
||
|
50% |
||
|
50% |
||
|
100% |
High priority applications run within HIGH_GROUP
, which is allocated 80% of CPU. Because HIGH_GROUP
is at level one, it gets priority for CPU utilization, but only up to 80% of CPU. This leaves a remaining 20% of CPU to be shared 50-50 by LOW_GROUP
and the MAINT_SUPLAN
at level 2. Any unused allocation from levels 1 and 2 are then available to OTHER_GROUPS
at level 3. Because OTHER_GROUPS
has no sibling consumer groups or subplans at its level, 100% is specified.
Within a particular level, CPU allocations are not fixed. If there is not sufficient load in a particular consumer group or subplan, residual CPU can be allocated to remaining consumer groups or subplans. Thus, when there is only one level, unused allocation by any consumer group or subplan can be redistributed to other "sibling" consumer groups or subplans. If there are multiple levels, then the unused allocation is distributed to the consumer groups or subplans at the next level. If the last level has unused allocations, these allocations can be redistributed to all other levels in proportion to their designated allocations.
As an example of redistribution of unused allocations from one level to another, if during a particular period, HIGH_GROUP
consumes only 25% of CPU, then 75% is available to be shared by LOW_GROUP
and MAINT_SUBPLAN
. Any unused portion of the 75% at level 2 is then made available to OTHER_GROUPS
at level 3. However, if OTHER_GROUPS
has no session activity at level 3, then the 75% at level 2 can be redistributed to all other consumer groups and subplans in the plan proportionally.
Parent topic: CPU
27.3.1.2 Utilization Limit
Use the UTILIZATION_LIMIT
attribute to impose an absolute upper limit on CPU utilization for a resource consumer group. This absolute limit overrides any redistribution of CPU within a plan.
In the previous scenario, suppose that due to inactivity elsewhere, LOW_GROUP
acquires 90% of CPU. Suppose that you do not want to allow LOW_GROUP
to use 90% of the server because you do not want non-critical sessions to inundate the CPUs. The UTILIZATION_LIMIT
attribute of resource plan directives can prevent this situation.
Setting the UTILIZATION_LIMIT
attribute is optional. If you omit this attribute for a consumer group, there is no limit on the amount of CPU that the consumer group can use. Therefore, if all the other applications are idle, a consumer group that does not have UTILIZATION_LIMIT
set can be allocated 100% of the CPU resources.
You can also use the UTILIZATION_LIMIT
attribute as the sole means of limiting CPU utilization for consumer groups, without specifying level limits.
Table 27-2 shows a variation of the previous plan. In this plan, using UTILIZATION_LIMIT
, CPU utilization is capped at 75% for LOW_GROUP
, 50% for MAINT_SUBPLAN
, and 75% for OTHER_GROUPS
. (Note that the sum of all utilization limits can exceed 100%. Each limit is applied independently.)
Table 27-2 A Three-Level Resource Plan with Utilization Limits
Consumer Group | Level 1 CPU Allocation | Level 2 CPU Allocation | Level 3 CPU Allocation | Utilization Limit |
---|---|---|---|---|
|
80% |
|||
|
50% |
75% |
||
|
50% |
50% |
||
|
100% |
75% |
In the example described in Table 27-2, if HIGH_GROUP
is using only 10% of the CPU at a given time, then the remaining 90% is available to LOW_GROUP
and the consumer groups in MAINT_SUBPLAN
at level 2. If LOW_GROUP
uses only 20% of the CPU, then 70% can be allocated to MAINT_SUBPLAN
. However, MAINT_SUBPLAN
has a UTILIZATION_LIMIT
of 50%. Therefore, even though more CPU resources are available, the server cannot allocate more than 50% of the CPU to the consumer groups that belong to the subplan MAINT_SUBPLAN
.
You can set UTILIZATION_LIMIT
for both a subplan and the consumer groups that the subplan contains. In such cases, the limit for a consumer group is computed using the limits specified for the subplan and that consumer group. For example, the MAINT_SUBPLAN
contains the consumer groups MAINT_GROUP1
and MAINT_GROUP2
. MAINT_GROUP1
has UTILIZATION_LIMIT
set to 40%. However, the limit for MAINT_SUBPLAN
is set to 50%. Therefore, the limit for consumer group MAINT_GROUP1
is computed as 40% of 50%, or 20%. For an example of how to compute UTILIZATION_LIMIT
for a consumer group when limits are specified for both the consumer group and the subplan to which the group belongs, see "Example 4 - Specifying a Utilization Limit for Consumer Groups and Subplans".
See Also:
Parent topic: CPU
27.3.2 Exadata I/O
Management attributes enable you to specify CPU resource allocation for Exadata I/O.
See Also:
The Exadata documentation for information about using management attributes for Exadata I/O
Parent topic: The Types of Resources Managed by the Resource Manager
27.3.3 Parallel Execution Servers
Resource Manager can manage usage of the available parallel execution servers for a database.
- Degree of Parallelism Limit
You can limit the maximum degree of parallelism for any operation within a consumer group. Use thePARALLEL_DEGREE_LIMIT_P1
directive attribute to specify the degree of parallelism for a consumer group. - Parallel Server Limit
Use thePARALLEL_SERVER_LIMIT
directive attribute to specify the maximum percentage of the parallel execution server pool that a particular consumer group can use. The number of parallel execution servers used by a particular consumer group is counted as the sum of the parallel execution servers used by all sessions in that consumer group. - Parallel Queue Timeout
ThePARALLEL_QUEUE_TIMEOUT
directive attribute enables you to specify the maximum time, in seconds, that a parallel statement can wait in the parallel statement queue before it is timed out.
Parent topic: The Types of Resources Managed by the Resource Manager
27.3.3.1 Degree of Parallelism Limit
You can limit the maximum degree of parallelism for any operation within a consumer group. Use the PARALLEL_DEGREE_LIMIT_P1
directive attribute to specify the degree of parallelism for a consumer group.
The degree of parallelism limit applies to one operation within a consumer group; it does not limit the total degree of parallelism across all operations within the consumer group. However, you can combine both the PARALLEL_DEGREE_LIMIT_P1
and the PARALLEL_SERVER_LIMIT
directive attributes to achieve the desired control. For more information about the PARALLEL_SERVER_LIMIT
attribute, see "Parallel Server Limit".
See Also:
Oracle Database VLDB and Partitioning Guide for more information about degree of parallelism in producer/consumer operations
Parent topic: Parallel Execution Servers
27.3.3.2 Parallel Server Limit
Use the PARALLEL_SERVER_LIMIT
directive attribute to specify the maximum percentage of the parallel execution server pool that a particular consumer group can use. The number of parallel execution servers used by a particular consumer group is counted as the sum of the parallel execution servers used by all sessions in that consumer group.
It is possible for a single consumer group to launch enough parallel statements to use all of the available parallel execution servers. If this happens when a high-priority parallel statement from a different consumer group is run, then no parallel execution servers are available to allocate to this group. You can avoid such a scenario by limiting the number of parallel execution servers that can be used by a particular consumer group. You can also set the directive PARALLEL_STMT_CRITICAL
to BYPASS_QUEUE
for the high-priority consumer group so that parallel statements from the consumer group bypass the parallel statement queue.
For example, assume that the total number of parallel execution servers is 32, as set by the PARALLEL_SERVERS_TARGET
initialization parameter, and the PARALLEL_SERVER_LIMIT
directive attribute for the consumer group MY_GROUP
is set to 50%. This consumer group can use a maximum of 50% of 32, or 16 parallel execution servers.
If your resource plan has management attributes (MGMT_P1
, MGMT_P2
, and so on), then a separate parallel statement queue is managed as a First In First Out (FIFO) queue for each management attribute.
If your resource plan does not have any management attributes, then a single parallel statement queue is managed as a FIFO queue.
In the case of an Oracle Real Application Clusters (Oracle RAC) environment, the target number of parallel execution servers is the sum of (PARALLEL_SERVER_LIMIT
* PARALLEL_SERVERS_TARGET
/ 100) across all Oracle RAC instances. If a consumer group is using the number of parallel execution servers computed above or more, then it has exceeded its limit, and its parallel statements will be queued.
If a consumer group does not have any parallel statements running within an Oracle RAC database, then the first parallel statement is allowed to exceed the limit specified by PARALLEL_SERVER_LIMIT
.
Note:
In an Oracle Real Application Clusters (Oracle RAC) environment, the PARALLEL_SERVER_LIMIT
attribute applies to the entire cluster and not to a single instance.
- Managing Parallel Statement Queuing Using Parallel Server Limit
ThePARALLEL_SERVER_LIMIT
attribute enables you to specify when parallel statements from a consumer group can be queued. Oracle Database maintains a separate parallel statement queue for each consumer group.
See Also:
-
"Managing Parallel Statement Queuing Using Parallel Server Limit"
-
Oracle Database VLDB and Partitioning Guide for information about parallel statement queuing
Parent topic: Parallel Execution Servers
27.3.3.2.1 Managing Parallel Statement Queuing Using Parallel Server Limit
The PARALLEL_SERVER_LIMIT
attribute enables you to specify when parallel statements from a consumer group can be queued. Oracle Database maintains a separate parallel statement queue for each consumer group.
A parallel statement from a consumer group is not run and instead is added to the parallel statement queue of that consumer group if the following conditions are met:
-
PARALLEL_DEGREE_POLICY
is set toAUTO
.Setting this initialization parameter to
AUTO
enables automatic degree of parallelism (Auto DOP), parallel statement queuing, and in-memory parallel execution.Note that parallel statements which have
PARALLEL_DEGREE_POLICY
set toMANUAL
orLIMITED
are executed immediately and are not added to the parallel statement queue. -
The number of active parallel execution servers across all consumer groups exceeds the
PARALLEL_SERVERS_TARGET
initialization parameter setting. This condition applies regardless of whether you specifyPARALLEL_SERVER_LIMIT
. IfPARALLEL_SERVER_LIMIT
is not specified, then it defaults to 100%. -
The sum of the number of active parallel execution servers for the consumer group and the degree of parallelism of the parallel statement exceeds the target number of active parallel execution servers.
The target number of active parallel execution servers is computed as follows:
PARALLEL_SERVER_LIMIT
/100 *PARALLEL_SERVERS_TARGET
Note:
Although parallel execution server usage is monitored for all sessions, the parallel execution server directive attributes you set affect only sessions for which parallel statement queuing is enabled (PARALLEL_DEGREE_POLICY
is set to AUTO
). If a session has the PARALLEL_DEGREE_POLICY
set to MANUAL
, parallel statements from this session are not queued. However, any parallel execution servers used by such sessions are included in the count that is used to determine the limit for PARALLEL_SERVER_LIMIT
. Even if this limit is exceeded, parallel statements from this session are not queued.
See Also:
Parent topic: Parallel Server Limit
27.3.3.3 Parallel Queue Timeout
The PARALLEL_QUEUE_TIMEOUT
directive attribute enables you to specify the maximum time, in seconds, that a parallel statement can wait in the parallel statement queue before it is timed out.
When you use parallel statement queuing, if the database does not have sufficient resources to execute a parallel statement, the statement is queued until the required resources become available. However, there is a chance that a parallel statement may be waiting in the parallel statement queue for longer than is desired. You can prevent such scenarios by specifying the maximum time a parallel statement can wait in the parallel statement queue.
The PARALLEL_QUEUE_TIMEOUT
attribute can be set for each consumer group. This attribute is applicable even if you do not specify other management attributes (MGMT_P1
, MGMT_P2
, and so on) in your resource plan.
See Also:
Oracle Database VLDB and Partitioning Guide for more information about parallel statement queuing
Note:
Because the parallel statement queue is clusterwide, all directives related to the parallel statement queue are also clusterwide.
You can control how a timed out parallel statement is handled by setting the PQ_TIMEOUT_ACTION
attribute for each consumer group. You can set this attribute to the following values:
-
CANCEL
- The statement execution ends with the errorORA-07454
. This is the default action for a timed out parallel statement. -
RUN
- The statement runs immediately. If there are not sufficient parallel servers to run the statement immediately, then the statement is downgraded to run at a lower degree of parallelism.
See Also:
"Example of Managing Parallel Statements Using Directive Attributes" for more information about the combined use of all the parallel execution server directive attributes
Parent topic: Parallel Execution Servers
27.3.4 Program Global Area (PGA)
To manage PGA resources, Resource Manager can limit the amount of PGA memory that can be allocated to each session in a particular consumer group.
To limit the PGA resources for each session in a consumer group, set the session_pga_limit
parameter in the package procedure DBMS_RESOURCE_MANAGER.CREATE_PLAN_DIRECTIVE
. The value of this parameter is the maximum amount of PGA memory, in megabytes, allowed for each session in the consumer group. If a session exceeds the limit set for its consumer group, then error ORA-10260 is raised. This limit includes parallel query slaves and job queue processes.
For example, poorly written PL/SQL code can consume an unbounded amount of PGA. You can use the session_pga_limit
parameter to limit sessions that run PL/SQL code to ensure that those sessions do not use an inordinate amount of PGA resource.
The following table illustrates a simple resource plan with PGA limits.
Table 27-3 A Simple Resource Plan with PGA Limits
Consumer Group | session_pga_limit Value |
---|---|
|
20 |
|
10 |
|
Null (unlimited) |
|
Null (unlimited) |
In this resource plan, high priority applications run within HIGH_GROUP
, and each session in that group is limited to 20 MB of PGA resource. The sessions used by the lower priority applications within LOW_GROUP
are limited to 10 MB of PGA resource. The sessions used for maintenance jobs within MAINT_SUPLAN
and other sessions within OTHER_GROUPS
can use unlimited PGA resource.
Note:
You can limit the PGA usage of a whole instance with thePGA_AGGREGATE_LIMIT
initialization parameter.
Parent topic: The Types of Resources Managed by the Resource Manager
27.3.5 Runaway Queries
Runaway sessions and calls can adversely impact overall performance if they are not managed properly. Resource Manager can take action when a session or call consumes more than a specified amount of CPU, physical I/O, logical I/O, or elapsed time. Resource Manager can either switch the session or call to a consumer group that is allocated a small amount of CPU or terminate the session or call.
Note:
Starting with Oracle Database 12c Release 2 (12.2), Resource Manager can also limit the amount of PGA memory that can be allocated to each session in a particular consumer group.
- Automatic Consumer Group Switching
You can control resource allocation by specifying criteria that, if met, causes the automatic switching of a session to a specified consumer group. - Canceling SQL and Terminating Sessions
You can use the Resource Manager to cancel long-running SQL queries or to terminate long-running sessions based on their amount of consumption of system resources, such as CPU and I/O. - Execution Time Limit
You can specify a maximum execution time allowed for an operation.
See Also:
"Program Global Area (PGA)"Parent topic: The Types of Resources Managed by the Resource Manager
27.3.5.1 Automatic Consumer Group Switching
You can control resource allocation by specifying criteria that, if met, causes the automatic switching of a session to a specified consumer group.
Typically, this method is used to switch a session from a high-priority consumer group—one that receives a high proportion of system resources—to a lower priority consumer group because that session exceeded the expected resource consumption for a typical session in the group.
See "Specifying Automatic Switching by Setting Resource Limits" for more information.
Parent topic: Runaway Queries
27.3.5.2 Canceling SQL and Terminating Sessions
You can use the Resource Manager to cancel long-running SQL queries or to terminate long-running sessions based on their amount of consumption of system resources, such as CPU and I/O.
The SQL queries canceled by the Resource Manager can be configured for quarantine using theDBMS_SQLQ
package subprograms, so that those queries are not allowed to run again.
See Also:
-
"Specifying Automatic Switching by Setting Resource Limits" for more information about how to configure the Resource Manager to cancel SQL queries or to terminate sessions based on their consumption of system resources
-
"Quarantine for Execution Plans for SQL Statements Consuming Excessive System Resources" for more information about how to configure quarantine settings for SQL queries using the
DBMS_SQLQ
package subprograms
Parent topic: Runaway Queries
27.3.5.3 Execution Time Limit
You can specify a maximum execution time allowed for an operation.
If the database estimates that an operation will run longer than the specified maximum execution time, then the operation is terminated with an error. This error can be trapped and the operation rescheduled.
Parent topic: Runaway Queries
27.3.6 Active Session Pool with Queuing
You can control the maximum number of concurrently active sessions allowed within a consumer group. This maximum defines the active session pool.
An active session is a session that is actively processing a transaction or SQL statement. Specifically, an active session is either in a transaction, holding a user enqueue, or has an open cursor and has not been idle for over 5 seconds. An active session is considered active even if it is blocked, for example waiting for an I/O request to complete. When the active session pool is full, a session that is trying to process a call is placed into a queue. When an active session completes, the first session in the queue can then be removed from the queue and scheduled for execution. You can also specify a period after which a session in the execution queue times out, causing the call to terminate with an error.
Active session limits should not be used for OLTP workloads. In addition, active session limits should not be used to implement connection pooling or parallel statement queuing.
To manage parallel statements, you must use parallel statement queuing with the PARALLEL_SERVER_LIMIT
attribute and management attributes (MGMT_P1
, MGMT_P2
, and so on).
Parent topic: The Types of Resources Managed by the Resource Manager
27.3.7 Undo Pool
You can specify an undo pool for each consumer group. An undo pool controls the total amount of undo for uncommitted transactions that can be generated by a consumer group.
When the total undo generated by a consumer group exceeds its undo limit, the current DML statement generating the undo is terminated. No other members of the consumer group can perform further data manipulation until undo space is freed from the pool.
Parent topic: The Types of Resources Managed by the Resource Manager
27.3.8 Idle Time Limit
You can specify an amount of time that a session can be idle, after which it is terminated.
You can also specify a more stringent idle time limit that applies to sessions that are idle and blocking other sessions.
Parent topic: The Types of Resources Managed by the Resource Manager
27.4 Creating a Simple Resource Plan
You can quickly create a simple resource plan that is adequate for many situations using the CREATE_SIMPLE_PLAN
procedure.
This procedure enables you to both create consumer groups and allocate resources to them by executing a single procedure call. Using this procedure, you are not required to invoke the procedures that are described in succeeding sections for creating a pending area, creating each consumer group individually, specifying resource plan directives, and so on.
You specify the following arguments for the CREATE_SIMPLE_PLAN
procedure:
Parameter | Description |
---|---|
|
Name of the plan |
|
Consumer group name for first group |
|
CPU resource allocated to this group |
|
Consumer group name for second group |
|
CPU resource allocated to this group |
|
Consumer group name for third group |
|
CPU resource allocated to this group |
|
Consumer group name for fourth group |
|
CPU resource allocated to this group |
|
Consumer group name for fifth group |
|
CPU resource allocated to this group |
|
Consumer group name for sixth group |
|
CPU resource allocated to this group |
|
Consumer group name for seventh group |
|
CPU resource allocated to this group |
|
Consumer group name for eighth group |
|
CPU resource allocated to this group |
You can specify up to eight consumer groups with this procedure. The only resource allocation method supported is CPU. The plan uses the EMPHASIS
CPU allocation policy (the default) and each consumer group uses the ROUND_ROBIN
scheduling policy (also the default). Each consumer group specified in the plan is allocated its CPU percentage at level 2. Also implicitly included in the plan are SYS_GROUP
(a system-defined group that is the initial consumer group for the users SYS
and SYSTEM
) and OTHER_GROUPS
. The SYS_GROUP
consumer group is allocated 100% of the CPU at level 1, and OTHER_GROUPS
is allocated 100% of the CPU at level 3.
Example: Creating a Simple Plan with the CREATE_SIMPLE_PLAN Procedure
The following PL/SQL block creates a simple resource plan with two user-specified consumer groups:
BEGIN DBMS_RESOURCE_MANAGER.CREATE_SIMPLE_PLAN(SIMPLE_PLAN => 'SIMPLE_PLAN1', CONSUMER_GROUP1 => 'MYGROUP1', GROUP1_PERCENT => 80, CONSUMER_GROUP2 => 'MYGROUP2', GROUP2_PERCENT => 20); END; /
Executing the preceding statements creates the following plan:
Consumer Group | Level 1 | Level 2 | Level 3 |
---|---|---|---|
|
100% |
- |
- |
|
- |
80% |
- |
|
- |
20% |
- |
|
- |
- |
100% |
See Also:
-
"Creating a Resource Plan" for more information on the
EMPHASIS
CPU allocation policy -
"Creating Resource Consumer Groups " for more information on the
ROUND_ROBIN
scheduling policy
Parent topic: Managing Resources with Oracle Database Resource Manager
27.5 Creating a Complex Resource Plan
When your situation calls for a more complex resource plan, you must create the plan, with its directives and consumer groups, in a staging area called the pending area, and then validate the plan before storing it in the data dictionary.
The following is a summary of the steps required to create a complex resource plan.
Note:
A complex resource plan is any resource plan that is not created with the DBMS_RESOURCE_MANAGER.CREATE_SIMPLE_PLAN
procedure.
Step 1: Create a pending area.
Step 2: Create, modify, or delete consumer groups.
Step 3: Map sessions to consumer groups.
Step 4: Create the resource plan.
Step 5: Create resource plan directives.
Step 6: Validate the pending area.
Step 7: Submit the pending area.
You use procedures in the DBMS_RESOURCE_MANAGER
PL/SQL package to complete these steps.
- About the Pending Area
The pending area is a staging area where you can create a new resource plan, update an existing plan, or delete a plan without affecting currently running applications. - Creating a Pending Area
You create a pending area with theCREATE_PENDING_AREA
procedure. - Creating Resource Consumer Groups
You create a resource consumer group using theCREATE_CONSUMER_GROUP
procedure. - Mapping Sessions to Consumer Groups
You can map sessions to consumer groups using theSET_CONSUMER_GROUP_MAPPING
procedure. - Creating a Resource Plan
You create a resource plan with theCREATE_PLAN
procedure. - Creating Resource Plan Directives
You use theCREATE_PLAN_DIRECTIVE
procedure to create resource plan directives. Each directive belongs to a plan or subplan and allocates resources to either a consumer group or subplan. - Validating the Pending Area
At any time when you are making changes in the pending area, you can callVALIDATE_PENDING_AREA
to ensure that the pending area is valid so far. - Submitting the Pending Area
After you have validated your changes, call theSUBMIT_PENDING_AREA
procedure to make your changes active. - Clearing the Pending Area
You can clear the pending area at any time using theCLEAR_PENDING_AREA
procedure.
See Also:
-
Oracle Database PL/SQL Packages and Types Reference for details on the
DBMS_RESOURCE_MANAGER
PL/SQL package.
Parent topic: Managing Resources with Oracle Database Resource Manager
27.5.1 About the Pending Area
The pending area is a staging area where you can create a new resource plan, update an existing plan, or delete a plan without affecting currently running applications.
When you create a pending area, the database initializes it and then copies existing plans into the pending area so that they can be updated.
Tip:
After you create the pending area, if you list all plans by querying the DBA_RSRC_PLANS
data dictionary view, you see two copies of each plan: one with the PENDING
status, and one without. The plans with the PENDING
status reflect any changes you made to the plans since creating the pending area. Pending changes can also be viewed for consumer groups using DBA_RSRC_CONSUMER_GROUPS
and for resource plan directives using DBA_RSRC_PLAN_DIRECTIVES
. See Resource Manager Data Dictionary Views for more information.
After you make changes in the pending area, you validate the pending area and then submit it. Upon submission, all pending changes are applied to the data dictionary, and the pending area is cleared and deactivated.
If you attempt to create, update, or delete a plan (or create, update, or delete consumer groups or resource plan directives) without first creating the pending area, you receive an error message.
Submitting the pending area does not activate any new plan that you create; it just stores new or updated plan information in the data dictionary. However, if you modify a plan that is currently active, the plan is reactivated with the new plan definition. See "Enabling Oracle Database Resource Manager and Switching Plans" for information about activating a resource plan.
When you create a pending area, no other users can create one until you submit or clear the pending area or log out.
Parent topic: Creating a Complex Resource Plan
27.5.2 Creating a Pending Area
You create a pending area with the CREATE_PENDING_AREA
procedure.
Example: Creating a pending area:
The following PL/SQL block creates and initializes a pending area:
BEGIN DBMS_RESOURCE_MANAGER.CREATE_PENDING_AREA(); END; /
Parent topic: Creating a Complex Resource Plan
27.5.3 Creating Resource Consumer Groups
You create a resource consumer group using the CREATE_CONSUMER_GROUP
procedure.
You can specify the following parameters:
Parameter | Description |
---|---|
|
Name to assign to the consumer group. |
|
Any comment. |
|
Deprecated. Use |
|
The resource allocation method for distributing CPU among sessions in the consumer group. The default is |
Example: Creating a Resource Consumer Group
The following PL/SQL block creates a consumer group called OLTP
with the default (ROUND-ROBIN
) method of allocating resources to sessions in the group:
BEGIN DBMS_RESOURCE_MANAGER.CREATE_CONSUMER_GROUP ( CONSUMER_GROUP => 'OLTP', COMMENT => 'OLTP applications'); END; /
See Also:
Parent topic: Creating a Complex Resource Plan
27.5.4 Mapping Sessions to Consumer Groups
You can map sessions to consumer groups using the SET_CONSUMER_GROUP_MAPPING
procedure.
You can specify the following parameters:
Parameter | Description |
---|---|
|
Session attribute type, specified as a package constant. |
|
Value of the attribute. |
|
Name of the consumer group. |
Example: Mapping a Session to a Consumer Group
The following PL/SQL block maps the oe
user to the OLTP
consumer group:
BEGIN DBMS_RESOURCE_MANAGER.SET_CONSUMER_GROUP_MAPPING( ATTRIBUTE => DBMS_RESOURCE_MANAGER.ORACLE_USER, VALUE => 'OE', CONSUMER_GROUP => 'OLTP'); END; /
See Also:
Parent topic: Creating a Complex Resource Plan
27.5.5 Creating a Resource Plan
You create a resource plan with the CREATE_PLAN
procedure.
You can specify the parameters shown in the following table. The first two parameters are required. The remainder are optional.
Parameter | Description |
---|---|
|
Name to assign to the plan. |
|
Any descriptive comment. |
|
Deprecated. Use |
|
Active session pool resource allocation method. |
|
Resource allocation method for specifying a limit on the |
|
Queuing resource allocation method. Controls the order in which queued inactive sessions are removed from the queue and added to the active session pool. |
|
Resource allocation method for specifying how much CPU each consumer group or subplan gets. |
|
If |
Example: Creating a Resource Plan
The following PL/SQL block creates a resource plan named DAYTIME
:
BEGIN DBMS_RESOURCE_MANAGER.CREATE_PLAN( PLAN => 'DAYTIME', COMMENT => 'More resources for OLTP applications'); END; /
- About the RATIO CPU Allocation Method
TheRATIO
method is an alternate CPU allocation method intended for simple plans that have only a single level of CPU allocation.
Parent topic: Creating a Complex Resource Plan
27.5.5.1 About the RATIO CPU Allocation Method
The RATIO
method is an alternate CPU allocation method intended for simple plans that have only a single level of CPU allocation.
Instead of percentages, you specify numbers corresponding to the ratio of CPU that you want to give to each consumer group. To use the RATIO
method, you set the MGMT_MTH
argument for the CREATE_PLAN
procedure to 'RATIO
'. See "Creating Resource Plan Directives " for an example of a plan that uses this method.
See Also:
Parent topic: Creating a Resource Plan
27.5.6 Creating Resource Plan Directives
You use the CREATE_PLAN_DIRECTIVE
procedure to create resource plan directives. Each directive belongs to a plan or subplan and allocates resources to either a consumer group or subplan.
Note:
The set of directives for a resource plan and its subplans can name a particular subplan only once.
You can specify directives for a particular consumer group in a top plan and its subplans. However, Oracle recommends that the set of directives for a resource plan and its subplans name a particular consumer group only once.
You can specify the following parameters:
Parameter | Description |
---|---|
|
Name of the resource plan to which the directive belongs. |
|
Name of the consumer group or subplan to which to allocate resources. |
|
Any comment. |
|
Deprecated. Use |
|
Deprecated. Use |
|
Deprecated. Use |
|
Deprecated. Use |
|
Deprecated. Use |
|
Deprecated. Use |
|
Deprecated. Use |
|
Deprecated. Use |
|
Specifies the maximum number of concurrently active sessions for a consumer group. Other sessions await execution in an inactive session queue. Default is |
|
Specifies time (in seconds) after which a session in an inactive session queue
(waiting for execution) times out and the call is terminated. Default is
|
|
Specifies a limit on the degree of parallelism for any operation. Default is |
|
Specifies the consumer group to which a session is switched if switch criteria are met. If the group name is If the group name is If the group name is If Note: The following consumer group names are reserved: |
|
Specifies the time (in CPU seconds) that a call can execute before an action is taken. Default is |
|
If The execution time estimate is obtained from the optimizer. The accuracy of the estimate is dependent on many factors, especially the quality of the optimizer statistics. In general, you should expect statistics to be no more accurate than ± 10 minutes. |
|
Specifies the maximum execution time (in CPU seconds) allowed for a call. If the optimizer estimates that a call will take longer than The accuracy of the estimate is dependent on many factors, especially the quality of the optimizer statistics. |
|
Sets a maximum in kilobytes (K) on the total amount of undo for uncommitted transactions that can be generated by a consumer group. Default is |
|
Indicates the maximum session idle time, in seconds. Default is |
|
Indicates the maximum session idle time of a blocking session, in seconds. Default is |
|
Deprecated. Use |
|
For a plan with the |
|
For |
|
For |
|
For |
|
For |
|
For |
|
For |
|
For |
|
Specifies the number of megabytes of physical I/O that a session can transfer (read and write) before an action is taken. Default is |
|
Specifies the number of physical I/O requests that a session can execute before an action is taken. Default is |
|
If |
|
Specifies the maximum time, in seconds, that a parallel statement can wait in the parallel statement queue before it is timed out. |
|
Specifies the maximum percentage of the parallel execution server pool that a particular consumer group can use. The number of parallel execution servers used by a particular consumer group is counted as the sum of the parallel execution servers used by all sessions in that consumer group. |
|
Specifies the maximum CPU utilization percentage permitted for the consumer group. This value overrides any level allocations for CPU ( |
|
Number of logical I/O requests that will trigger the action specified by |
|
Elapsed time, in seconds, that will trigger the action specified by |
|
Allocates resources among pluggable databases (PDBs) in a multitenant container database (CDB). Also allocates resources among consumer groups in a PDB. |
|
Specifies whether parallel statements from the consumer group are critical. When When |
|
Specifies the maximum amount of PGA memory, in megabytes, that can be allocated to each session in a particular consumer group. If a session exceeds the limit, then its process is terminated with an |
Example 1
The following PL/SQL block creates a resource plan directive for plan DAYTIME
. (It assumes that the DAYTIME
plan and OLTP
consumer group are already created in the pending area.)
BEGIN DBMS_RESOURCE_MANAGER.CREATE_PLAN_DIRECTIVE ( PLAN => 'DAYTIME', GROUP_OR_SUBPLAN => 'OLTP', COMMENT => 'OLTP group', MGMT_P1 => 75); END; /
This directive assigns 75% of CPU resources to the OLTP
consumer group at level 1.
You can also create the REPORTING
consumer group, and then execute the following PL/SQL block:
BEGIN DBMS_RESOURCE_MANAGER.CREATE_PLAN_DIRECTIVE ( PLAN => 'DAYTIME', GROUP_OR_SUBPLAN => 'REPORTING', COMMENT => 'Reporting group', MGMT_P1 => 15, PARALLEL_DEGREE_LIMIT_P1 => 8, ACTIVE_SESS_POOL_P1 => 4, SESSION_PGA_LIMIT => 20); DBMS_RESOURCE_MANAGER.CREATE_PLAN_DIRECTIVE ( PLAN => 'DAYTIME', GROUP_OR_SUBPLAN => 'OTHER_GROUPS', COMMENT => 'This one is required', MGMT_P1 => 10); END; /
In this plan, consumer group REPORTING
has a maximum degree of parallelism of 8 for any operation, while none of the other consumer groups are limited in their degree of parallelism. In addition, the REPORTING
group has a maximum of 4 concurrently active sessions. Each session can use a maximum of 20 MB of PGA memory.
Example 2
This example uses the RATIO
method to allocate CPU, which uses ratios instead of percentages. Suppose your application suite offers three service levels to clients: Gold, Silver, and Bronze. You create three consumer groups named GOLD_CG
, SILVER_CG
, and BRONZE_CG
, and you create the following resource plan:
BEGIN DBMS_RESOURCE_MANAGER.CREATE_PLAN (PLAN => 'SERVICE_LEVEL_PLAN', MGMT_MTH => 'RATIO', COMMENT => 'Plan that supports three service levels'); DBMS_RESOURCE_MANAGER.CREATE_PLAN_DIRECTIVE (PLAN => 'SERVICE_LEVEL_PLAN', GROUP_OR_SUBPLAN => 'GOLD_CG', COMMENT => 'Gold service level customers', MGMT_P1 => 10); DBMS_RESOURCE_MANAGER.CREATE_PLAN_DIRECTIVE (PLAN => 'SERVICE_LEVEL_PLAN', GROUP_OR_SUBPLAN => 'SILVER_CG', COMMENT => 'Silver service level customers', MGMT_P1 => 5); DBMS_RESOURCE_MANAGER.CREATE_PLAN_DIRECTIVE (PLAN => 'SERVICE_LEVEL_PLAN', GROUP_OR_SUBPLAN => 'BRONZE_CG', COMMENT => 'Bronze service level customers', MGMT_P1 => 2); DBMS_RESOURCE_MANAGER.CREATE_PLAN_DIRECTIVE (PLAN => 'SERVICE_LEVEL_PLAN', GROUP_OR_SUBPLAN => 'OTHER_GROUPS', COMMENT => 'Lowest priority sessions', MGMT_P1 => 1); END; /
The ratio of CPU allocation is 10:5:2:1 for the GOLD_CG
, SILVER_CG
, BRONZE_CG
, and OTHER_GROUPS
consumer groups, respectively.
If sessions exist only in the GOLD_CG
and SILVER_CG
consumer groups, then the ratio of CPU allocation is 10:5 between the two groups.
- Conflicting Resource Plan Directives
Although this is allowed, Oracle strongly recommends that you avoid referencing the same consumer group from a top plan and any of its subplans.
Parent topic: Creating a Complex Resource Plan
27.5.6.1 Conflicting Resource Plan Directives
Although this is allowed, Oracle strongly recommends that you avoid referencing the same consumer group from a top plan and any of its subplans.
You may have occasion to reference the same consumer group from the top plan and any number of subplans. This results in multiple resource plan directives referring to the same consumer group.
Similarly, when multiple resource plan directives refer to the same consumer group, they have conflicting directives. Although this is allowed, Oracle strongly recommends that you avoid multiple resource plan directives that refer to the same consumer group.
Parent topic: Creating Resource Plan Directives
27.5.7 Validating the Pending Area
At any time when you are making changes in the pending area, you can call VALIDATE_PENDING_AREA
to ensure that the pending area is valid so far.
The following rules must be adhered to, and are checked by the validate procedure:
-
No plan can contain any loops. A loop occurs when a subplan contains a directive that references a plan that is above the subplan in the plan hierarchy. For example, a subplan cannot reference the top plan.
-
All plans and resource consumer groups referred to by plan directives must exist.
-
All plans must have plan directives that point to either plans or resource consumer groups.
-
All percentages in any given level must not add up to greater than 100.
-
A plan that is currently being used as a top plan by an active instance cannot be deleted.
-
The following parameters can appear only in plan directives that refer to resource consumer groups, not other resource plans:
-
ACTIVE_SESS_POOL_P1
-
MAX_EST_EXEC_TIME
-
MAX_IDLE_BLOCKER_TIME
-
MAX_IDLE_TIME
-
PARALLEL_DEGREE_LIMIT_P1
-
QUEUEING_P1
-
SESSION_PGA_LIMIT
-
SWITCH_ESTIMATE
-
SWITCH_FOR_CALL
-
SWITCH_GROUP
-
SWITCH_IO_MEGABYTES
-
SWITCH_IO_REQS
-
SWITCH_TIME
-
UNDO_POOL
-
UTILIZATION_LIMIT
-
-
There can be no more than 28 resource consumer groups in any active plan. Also, at most, a plan can have 28 children.
-
Plans and resource consumer groups cannot have the same name.
-
There must be a plan directive for
OTHER_GROUPS
somewhere in any active plan. This ensures that a session that is not part of any of the consumer groups included in the currently active plan is allocated resources (as specified by the directive forOTHER_GROUPS
).
VALIDATE_PENDING_AREA
raises an error if any of the preceding rules are violated. You can then make changes to fix any problems and call the procedure again.
It is possible to create "orphan" consumer groups that have no plan directives referring to them. This allows the creation of consumer groups that will not currently be used, but might be part of some plan to be implemented in the future.
Example: Validating the Pending Area:
The following PL/SQL block validates the pending area.
BEGIN DBMS_RESOURCE_MANAGER.VALIDATE_PENDING_AREA(); END; /
See Also:
Parent topic: Creating a Complex Resource Plan
27.5.8 Submitting the Pending Area
After you have validated your changes, call the SUBMIT_PENDING_AREA
procedure to make your changes active.
The submit procedure also performs validation, so you do not necessarily need to make separate calls to the validate procedure. However, if you are making major changes to plans, debugging problems is often easier if you incrementally validate your changes. No changes are submitted (made active) until validation is successful on all of the changes in the pending area.
The SUBMIT_PENDING_AREA
procedure clears (deactivates) the pending area after successfully validating and committing the changes.
Note:
A call to SUBMIT_PENDING_AREA
might fail even if VALIDATE_PENDING_AREA
succeeds. This can happen if, for example, a plan being deleted is loaded by an instance after a call to VALIDATE_PENDING_AREA
, but before a call to SUBMIT_PENDING_AREA
.
Example: Submitting the Pending Area:
The following PL/SQL block submits the pending area:
BEGIN DBMS_RESOURCE_MANAGER.SUBMIT_PENDING_AREA(); END; /
See Also:
Parent topic: Creating a Complex Resource Plan
27.5.9 Clearing the Pending Area
You can clear the pending area at any time using the CLEAR_PENDING_AREA
procedure.
This PL/SQL block causes all of your changes to be cleared from the pending area and deactivates the pending area:
BEGIN DBMS_RESOURCE_MANAGER.CLEAR_PENDING_AREA(); END; /
After calling CLEAR_PENDING_AREA
, you must call the CREATE_PENDING_AREA
procedure before you can again attempt to make changes.
See Also:
Parent topic: Creating a Complex Resource Plan
27.6 Enabling Oracle Database Resource Manager and Switching Plans
You enable Oracle Database Resource Manager (the Resource Manager) by setting the RESOURCE_MANAGER_PLAN
initialization parameter. This parameter specifies the top plan, identifying the plan to be used for the current instance. If no plan is specified with this parameter, the Resource Manager is not enabled.
By default the Resource Manager is not enabled, except in the following situations:
-
During preconfigured maintenance windows, described later in this section.
-
When Oracle Database In-Memory is enabled by setting the
INMEMORY_SIZE
initialization parameter to a value greater than 0.
The following statement in a text initialization parameter file activates the Resource Manager upon database startup and sets the top plan as mydb_plan
.
RESOURCE_MANAGER_PLAN = mydb_plan
You can also activate or deactivate the Resource Manager, or change the current top plan, using the DBMS_RESOURCE_MANAGER.SWITCH_PLAN
package procedure or the ALTER SYSTEM
statement.
The following SQL statement sets the top plan to mydb_plan
, and activates the Resource Manager if it is not already active:
ALTER SYSTEM SET RESOURCE_MANAGER_PLAN = 'mydb_plan';
An error message is returned if the specified plan does not exist in the data dictionary.
Automatic Enabling of the Resource Manager by Oracle Scheduler Windows
The Resource Manager automatically activates if an Oracle Scheduler window that specifies a resource plan opens. When the Scheduler window closes, the resource plan associated with the window is disabled, and the resource plan that was running before the Scheduler window opened is reenabled. (If no resource plan was enabled before the window opened, then the Resource Manager is disabled.) In an Oracle Real Application Clusters environment, a Scheduler window applies to all instances, so the window's resource plan is enabled on every instance.
Note that by default a set of automated maintenance tasks run during maintenance windows, which are predefined Scheduler windows that are members of the MAINTENANCE_WINDOW_GROUP
window group and which specify the DEFAULT_MAINTENANCE_PLAN
resource plan. Thus, the Resource Manager activates by default during maintenance windows. You can modify these maintenance windows to use a different resource plan, if desired.
Note:
If you change the plan associated with maintenance windows, then ensure that you include the subplan ORA$AUTOTASK
in the new plan.
See Also:
Disabling Plan Switches by Oracle Scheduler Windows
In some cases, the automatic change of Resource Manager plans at Scheduler window boundaries may be undesirable. For example, if you have an important task to finish, and if you set the Resource Manager plan to give your task priority, then you expect that the plan will remain the same until you change it. However, because a Scheduler window could activate after you have set your plan, the Resource Manager plan might change while your task is running.
To prevent this situation, you can set the RESOURCE_MANAGER_PLAN
initialization parameter to the name of the plan that you want for the system and prepend "FORCE:
" to the name, as shown in the following SQL statement:
ALTER SYSTEM SET RESOURCE_MANAGER_PLAN = 'FORCE:mydb_plan';
Using the prefix FORCE:
indicates that the current resource plan can be changed only when the database administrator changes the value of the RESOURCE_MANAGER_PLAN
initialization parameter. This restriction can be lifted by rerunning the command without preceding the plan name with "FORCE:
".
The DBMS_RESOURCE_MANAGER.SWITCH_PLAN
package procedure has a similar capability.
See Also:
Oracle Database PL/SQL Packages and Types Reference for more information on DBMS_RESOURCE_MANAGER.SWITCH_PLAN
.
Disabling the Resource Manager
To disable the Resource Manager, complete the following steps:
Parent topic: Managing Resources with Oracle Database Resource Manager
27.7 Putting It All Together: Oracle Database Resource Manager Examples
Examples illustrate how to allocate resources with Resource Manager.
- Multilevel Plan Example
An example illustrates a multilevel plan. - Examples of Using the Utilization Limit Attribute
You can use theUTILIZATION_LIMIT
directive attribute to limit the CPU utilization for applications. One of the most common scenarios in which this attribute can be used is for database consolidation. - Example of Using Several Resource Allocation Methods
An example illustrates using several resource allocation methods. - Example of Managing Parallel Statements Using Directive Attributes
An example illustrates managing parallel statements using directive attributes. - An Oracle-Supplied Mixed Workload Plan
Oracle Database includes a predefined resource plan,MIXED_WORKLOAD_PLAN
, that prioritizes interactive operations over batch operations, and includes the required subplans and consumer groups recommended by Oracle.
Parent topic: Managing Resources with Oracle Database Resource Manager
27.7.1 Multilevel Plan Example
An example illustrates a multilevel plan.
The following PL/SQL block creates a multilevel plan as illustrated in Figure 27-3. Default resource allocation method settings are used for all plans and resource consumer groups.
BEGIN DBMS_RESOURCE_MANAGER.CREATE_PENDING_AREA(); DBMS_RESOURCE_MANAGER.CREATE_PLAN(PLAN => 'bugdb_plan', COMMENT => 'Resource plan/method for bug users sessions'); DBMS_RESOURCE_MANAGER.CREATE_PLAN(PLAN => 'maildb_plan', COMMENT => 'Resource plan/method for mail users sessions'); DBMS_RESOURCE_MANAGER.CREATE_PLAN(PLAN => 'mydb_plan', COMMENT => 'Resource plan/method for bug and mail users sessions'); DBMS_RESOURCE_MANAGER.CREATE_CONSUMER_GROUP(CONSUMER_GROUP => 'Online_group', COMMENT => 'Resource consumer group/method for online bug users sessions'); DBMS_RESOURCE_MANAGER.CREATE_CONSUMER_GROUP(CONSUMER_GROUP => 'Batch_group', COMMENT => 'Resource consumer group/method for batch job bug users sessions'); DBMS_RESOURCE_MANAGER.CREATE_CONSUMER_GROUP(CONSUMER_GROUP => 'Bug_Maint_group', COMMENT => 'Resource consumer group/method for users sessions for bug db maint'); DBMS_RESOURCE_MANAGER.CREATE_CONSUMER_GROUP(CONSUMER_GROUP => 'Users_group', COMMENT => 'Resource consumer group/method for mail users sessions'); DBMS_RESOURCE_MANAGER.CREATE_CONSUMER_GROUP(CONSUMER_GROUP => 'Postman_group', COMMENT => 'Resource consumer group/method for mail postman'); DBMS_RESOURCE_MANAGER.CREATE_CONSUMER_GROUP(CONSUMER_GROUP => 'Mail_Maint_group', COMMENT => 'Resource consumer group/method for users sessions for mail db maint'); DBMS_RESOURCE_MANAGER.CREATE_PLAN_DIRECTIVE(PLAN => 'bugdb_plan', GROUP_OR_SUBPLAN => 'Online_group', COMMENT => 'online bug users sessions at level 1', MGMT_P1 => 80, MGMT_P2=> 0); DBMS_RESOURCE_MANAGER.CREATE_PLAN_DIRECTIVE(PLAN => 'bugdb_plan', GROUP_OR_SUBPLAN => 'Batch_group', COMMENT => 'batch bug users sessions at level 1', MGMT_P1 => 20, MGMT_P2 => 0, PARALLEL_DEGREE_LIMIT_P1 => 8); DBMS_RESOURCE_MANAGER.CREATE_PLAN_DIRECTIVE(PLAN => 'bugdb_plan', GROUP_OR_SUBPLAN => 'Bug_Maint_group', COMMENT => 'bug maintenance users sessions at level 2', MGMT_P1 => 0, MGMT_P2 => 100); DBMS_RESOURCE_MANAGER.CREATE_PLAN_DIRECTIVE(PLAN => 'bugdb_plan', GROUP_OR_SUBPLAN => 'OTHER_GROUPS', COMMENT => 'all other users sessions at level 3', MGMT_P1 => 0, MGMT_P2 => 0, MGMT_P3 => 100); DBMS_RESOURCE_MANAGER.CREATE_PLAN_DIRECTIVE(PLAN => 'maildb_plan', GROUP_OR_SUBPLAN => 'Postman_group', COMMENT => 'mail postman at level 1', MGMT_P1 => 40, MGMT_P2 => 0); DBMS_RESOURCE_MANAGER.CREATE_PLAN_DIRECTIVE(PLAN => 'maildb_plan', GROUP_OR_SUBPLAN => 'Users_group', COMMENT => 'mail users sessions at level 2', MGMT_P1 => 0, MGMT_P2 => 80); DBMS_RESOURCE_MANAGER.CREATE_PLAN_DIRECTIVE(PLAN => 'maildb_plan', GROUP_OR_SUBPLAN => 'Mail_Maint_group', COMMENT => 'mail maintenance users sessions at level 2', MGMT_P1 => 0, MGMT_P2 => 20); DBMS_RESOURCE_MANAGER.CREATE_PLAN_DIRECTIVE(PLAN => 'maildb_plan', GROUP_OR_SUBPLAN => 'OTHER_GROUPS', COMMENT => 'all other users sessions at level 3', MGMT_P1 => 0, MGMT_P2 => 0, MGMT_P3 => 100); DBMS_RESOURCE_MANAGER.CREATE_PLAN_DIRECTIVE(PLAN => 'mydb_plan', GROUP_OR_SUBPLAN => 'maildb_plan', COMMENT=> 'all mail users sessions at level 1', MGMT_P1 => 30); DBMS_RESOURCE_MANAGER.CREATE_PLAN_DIRECTIVE(PLAN => 'mydb_plan', GROUP_OR_SUBPLAN => 'bugdb_plan', COMMENT => 'all bug users sessions at level 1', MGMT_P1 => 70); DBMS_RESOURCE_MANAGER.VALIDATE_PENDING_AREA(); DBMS_RESOURCE_MANAGER.SUBMIT_PENDING_AREA(); END; /
The preceding call to VALIDATE_PENDING_AREA
is optional because the validation is implicitly performed in SUBMIT_PENDING_AREA
.
In this plan schema, CPU resources are allocated as follows:
-
Under
mydb_plan
, 30% of CPU is allocated to themaildb_plan
subplan, and 70% is allocated to thebugdb_plan
subplan. Both subplans are at level 1. Becausemydb_plan
itself has no levels below level 1, any resource allocations that are unused by either subplan at level 1 can be used by its sibling subplan. Thus, ifmaildb_plan
uses only 20% of CPU, then 80% of CPU is available tobugdb_plan
. -
maildb_plan
andbugdb_plan
define allocations at levels 1, 2, and 3. The levels in these subplans are independent of levels in their parent plan,mydb_plan
. That is, all plans and subplans in a plan schema have their own level 1, level 2, level 3, and so on. -
Of the 30% of CPU allocated to
maildb_plan
, 40% of that amount (effectively 12% of total CPU) is allocated toPostman_group
at level 1. BecausePostman_group
has no siblings at level 1, there is an implied 60% remaining at level 1. This 60% is then shared byUsers_group
andMail_Maint_group
at level 2, at 80% and 20%, respectively. In addition to this 60%,Users_group
andMail_Maint_group
can also use any of the 40% not used byPostman_group
at level 1. -
CPU resources not used by either
Users_group
orMail_Maint_group
at level 2 are allocated toOTHER_GROUPS
, because in multilevel plans, unused resources are reallocated to consumer groups or subplans at the next lower level, not to siblings at the same level. Thus, ifUsers_group
uses only 70% instead of 80%, the remaining 10% cannot be used byMail_Maint_group
. That 10% is available only toOTHER_GROUPS
at level 3. -
The 70% of CPU allocated to the
bugdb_plan
subplan is allocated to its consumer groups in a similar fashion. If eitherOnline_group
orBatch_group
does not use its full allocation, the remainder may be used byBug_Maint_group
. IfBug_Maint_group
does not use all of that allocation, the remainder goes toOTHER_GROUPS
.
27.7.2 Examples of Using the Utilization Limit Attribute
You can use the UTILIZATION_LIMIT
directive attribute to limit the CPU utilization for applications. One of the most common scenarios in which this attribute can be used is for database consolidation.
During database consolidation, you may need to be able to do the following:
-
Manage the performance impact that one application can have on another.
One method of managing this performance impact is to create a consumer group for each application and allocate resources to each consumer group.
-
Limit the utilization of each application.
Typically, in addition to allocating a specific percentage of the CPU resources to each consumer group, you may need to limit the maximum CPU utilization for each group. This limit prevents a consumer group from using all of the CPU resources when all the other consumer groups are idle.
In some cases, you may want all application users to experience consistent performance regardless of the workload from other applications. This can be achieved by specifying a utilization limit for each consumer group in a resource plan.
The following examples demonstrate how to use the UTILIZATION_LIMIT
resource plan directive attribute to:
-
Restrict total database CPU utilization
-
Quarantine runaway queries
-
Limit CPU usage for applications
-
Limit CPU utilization during maintenance windows
Example 1 - Restricting Overall Database CPU Utilization
In this example, regardless of database load, system workload from Oracle Database never exceeds 90% of CPU, leaving 10% of CPU for other applications sharing the server.
BEGIN DBMS_RESOURCE_MANAGER.CREATE_PENDING_AREA(); DBMS_RESOURCE_MANAGER.CREATE_PLAN( PLAN => 'MAXCAP_PLAN', COMMENT => 'Limit overall database CPU'); DBMS_RESOURCE_MANAGER.CREATE_PLAN_DIRECTIVE( PLAN => 'MAXCAP_PLAN', GROUP_OR_SUBPLAN => 'OTHER_GROUPS', COMMENT => 'This group is mandatory', UTILIZATION_LIMIT => 90); DBMS_RESOURCE_MANAGER.VALIDATE_PENDING_AREA(); DBMS_RESOURCE_MANAGER.SUBMIT_PENDING_AREA(); END; /
Because there is no plan directive other than the one for OTHER_GROUPS
, all sessions are mapped to OTHER_GROUPS
.
Example 2 - Quarantining Runaway Queries
In this example, runaway queries are switched to a consumer group with a utilization limit of 20%, limiting the amount of resources that they can consume until you can intervene. A runaway query is characterized here as one that takes more than 10 minutes of CPU time. Assume that session mapping rules start all sessions in START_GROUP
.
BEGIN DBMS_RESOURCE_MANAGER.CREATE_PENDING_AREA(); DBMS_RESOURCE_MANAGER.CREATE_CONSUMER_GROUP ( CONSUMER_GROUP => 'START_GROUP', COMMENT => 'Sessions start here'); DBMS_RESOURCE_MANAGER.CREATE_CONSUMER_GROUP ( CONSUMER_GROUP => 'QUARANTINE_GROUP', COMMENT => 'Sessions switched here to quarantine them'); DBMS_RESOURCE_MANAGER.CREATE_PLAN( PLAN => 'Quarantine_plan', COMMENT => 'Quarantine runaway queries'); DBMS_RESOURCE_MANAGER.CREATE_PLAN_DIRECTIVE( PLAN => 'Quarantine_plan', GROUP_OR_SUBPLAN => 'START_GROUP', COMMENT => 'Max CPU 10 minutes before switch', MGMT_P1 => 75, switch_group => 'QUARANTINE_GROUP', switch_time => 600); DBMS_RESOURCE_MANAGER.CREATE_PLAN_DIRECTIVE( PLAN => 'Quarantine_plan', GROUP_OR_SUBPLAN => 'OTHER_GROUPS', COMMENT => 'Mandatory', MGMT_P1 => 25); DBMS_RESOURCE_MANAGER.CREATE_PLAN_DIRECTIVE( PLAN => 'Quarantine_plan', GROUP_OR_SUBPLAN => 'QUARANTINE_GROUP', COMMENT => 'Limited CPU', MGMT_P2 => 100, UTILIZATION_LIMIT => 20); DBMS_RESOURCE_MANAGER.VALIDATE_PENDING_AREA(); DBMS_RESOURCE_MANAGER.SUBMIT_PENDING_AREA(); END; /
Note:
Although you could set the utilization limit to zero for QUARANTINE_GROUP
, thus completely quarantining runaway queries, it is recommended that you avoid doing this. If the runaway query is holding any resources—PGA memory, locks, and so on—required by any other session, then a zero allocation setting could lead to a deadlock.
Example 3 - Limiting CPU for Applications
In this example, assume that mapping rules map application sessions into one of four application groups. Each application group is allocated a utilization limit of 30%. This limits CPU utilization of any one application to 30%. The sum of the UTILIZATION_LIMIT
values exceeds 100%, which is permissible and acceptable in a situation where all applications are not active simultaneously.
BEGIN DBMS_RESOURCE_MANAGER.CREATE_PENDING_AREA(); DBMS_RESOURCE_MANAGER.CREATE_CONSUMER_GROUP( CONSUMER_GROUP => 'APP1_GROUP', COMMENT => 'Apps group 1'); DBMS_RESOURCE_MANAGER.CREATE_CONSUMER_GROUP ( CONSUMER_GROUP => 'APP2_GROUP', COMMENT => 'Apps group 2'); DBMS_RESOURCE_MANAGER.CREATE_CONSUMER_GROUP ( CONSUMER_GROUP => 'APP3_GROUP', COMMENT => 'Apps group 3'); DBMS_RESOURCE_MANAGER.CREATE_CONSUMER_GROUP ( CONSUMER_GROUP => 'APP4_GROUP', COMMENT => 'Apps group 4'); DBMS_RESOURCE_MANAGER.CREATE_PLAN( PLAN => 'apps_plan', COMMENT => 'Application consolidation'); DBMS_RESOURCE_MANAGER.CREATE_PLAN_DIRECTIVE ( PLAN => 'apps_plan', GROUP_OR_SUBPLAN => 'APP1_GROUP', COMMENT => 'Apps group 1', UTILIZATION_LIMIT => 30); DBMS_RESOURCE_MANAGER.CREATE_PLAN_DIRECTIVE ( PLAN => 'apps_plan', GROUP_OR_SUBPLAN => 'APP2_GROUP', COMMENT => 'Apps group 2', UTILIZATION_LIMIT => 30); DBMS_RESOURCE_MANAGER.CREATE_PLAN_DIRECTIVE ( PLAN => 'apps_plan', GROUP_OR_SUBPLAN => 'APP3_GROUP', COMMENT => 'Apps group 3', UTILIZATION_LIMIT => 30); DBMS_RESOURCE_MANAGER.CREATE_PLAN_DIRECTIVE ( PLAN => 'apps_plan', GROUP_OR_SUBPLAN => 'APP4_GROUP', COMMENT => 'Apps group 4', UTILIZATION_LIMIT => 30); DBMS_RESOURCE_MANAGER.CREATE_PLAN_DIRECTIVE ( PLAN => 'apps_plan', GROUP_OR_SUBPLAN => 'OTHER_GROUPS', COMMENT => 'Mandatory', UTILIZATION_LIMIT => 20); DBMS_RESOURCE_MANAGER.VALIDATE_PENDING_AREA(); DBMS_RESOURCE_MANAGER.SUBMIT_PENDING_AREA(); END; /
If all four application groups can fully use the CPU allocated to them (30% in this case), then the minimum CPU that is allocated to each application group is computed as a ratio of the application group's limit to the total of the limits of all application groups. In this example, all four application groups are allocated a utilization limit of 30%. Therefore, when all four groups fully use their limits, the CPU allocation to each group is 30/(30+30+30+30) = 25%.
Example 4 - Specifying a Utilization Limit for Consumer Groups and Subplans
The following example describes how the utilization limit is computed for scenarios, such as the one in Figure 27-4, where you set UTILIZATION_LIMIT
for a subplan and for consumer groups within the subplan. For simplicity, the requirement to include the OTHER_GROUPS
consumer group is ignored, and resource plan directives are not shown, even though they are part of the plan.
Figure 27-4 Resource Plan with Maximum Utilization for Subplan and Consumer Groups
Description of "Figure 27-4 Resource Plan with Maximum Utilization for Subplan and Consumer Groups"
The following PL/SQL block creates the plan described in Figure 27-4.
BEGIN DBMS_RESOURCE_MANAGER.CREATE_PENDING_AREA(); DBMS_RESOURCE_MANAGER.CREATE_CONSUMER_GROUP ( CONSUMER_GROUP => 'APP1_GROUP', COMMENT => 'Group for application #1'); DBMS_RESOURCE_MANAGER.CREATE_CONSUMER_GROUP ( CONSUMER_GROUP => 'APP2_OLTP_GROUP', COMMENT => 'Group for OLTP activity in application #2'); DBMS_RESOURCE_MANAGER.CREATE_CONSUMER_GROUP ( CONSUMER_GROUP => 'APP2_ADHOC_GROUP', COMMENT => 'Group for ad-hoc queries in application #2'); DBMS_RESOURCE_MANAGER.CREATE_CONSUMER_GROUP ( CONSUMER_GROUP => 'APP2_REPORT_GROUP', COMMENT => 'Group for reports in application #2'); DBMS_RESOURCE_MANAGER.CREATE_PLAN( PLAN => 'APPS_PLAN', COMMENT => 'Plan for managing 3 applications'); DBMS_RESOURCE_MANAGER.CREATE_PLAN( PLAN => 'APP2_SUBPLAN', COMMENT => 'Subplan for managing application #2', SUB_PLAN => TRUE); DBMS_RESOURCE_MANAGER.CREATE_PLAN( PLAN => 'APP2_REPORTS_SUBPLAN', COMMENT => 'Subplan for managing reports in application #2', SUB_PLAN => TRUE); DBMS_RESOURCE_MANAGER.CREATE_PLAN_DIRECTIVE ( PLAN => 'APPS_PLAN', GROUP_OR_SUBPLAN => 'APP1_GROUP', COMMENT => 'Limit CPU for application #1 to 40%', UTILIZATION_LIMIT => 40); DBMS_RESOURCE_MANAGER.CREATE_PLAN_DIRECTIVE ( PLAN => 'APPS_PLAN', GROUP_OR_SUBPLAN => 'APP2_SUBPLAN', COMMENT => 'Limit CPU for application #2 to 40%', UTILIZATION_LIMIT => 40); DBMS_RESOURCE_MANAGER.CREATE_PLAN_DIRECTIVE ( PLAN => 'APP2_SUBPLAN', GROUP_OR_SUBPLAN => 'APP2_OLTP_GROUP', COMMENT => 'Limit CPU for OLTP to 90% of application #2', UTILIZATION_LIMIT => 90); DBMS_RESOURCE_MANAGER.CREATE_PLAN_DIRECTIVE ( PLAN => 'APP2_SUBPLAN', GROUP_OR_SUBPLAN => 'APP2_REPORTS_SUBPLAN', COMMENT => 'Subplan for ad-hoc and normal reports for application #2'); DBMS_RESOURCE_MANAGER.CREATE_PLAN_DIRECTIVE ( PLAN => 'APP2_REPORTS_SUBPLAN', GROUP_OR_SUBPLAN => 'APP2_ADHOC_GROUP', COMMENT => 'Limit CPU for ad-hoc queries to 50% of application #2 reports', UTILIZATION_LIMIT => 50); DBMS_RESOURCE_MANAGER.CREATE_PLAN_DIRECTIVE ( PLAN => 'APP2_REPORTS_SUBPLAN', GROUP_OR_SUBPLAN => 'APP2_REPORT_GROUP', COMMENT => 'Limit CPU for reports to 50% of application #2 reports', UTILIZATION_LIMIT => 50); DBMS_RESOURCE_MANAGER.CREATE_PLAN_DIRECTIVE ( PLAN => 'APPS_PLAN', GROUP_OR_SUBPLAN => 'OTHER_GROUPS', COMMENT => 'No directives for default users'); DBMS_RESOURCE_MANAGER.VALIDATE_PENDING_AREA(); DBMS_RESOURCE_MANAGER.SUBMIT_PENDING_AREA(); END; /
In this example, the maximum CPU utilization for the consumer group APP1_GROUP
and subplan APP2_SUBPLAN
is set to 40%. The limit for the consumer groups APP2_ADHOC_GROUP
and APP2_REPORT_GROUP
is set to 50%.
Because there is no limit specified for the subplan APP2_REPORTS_SUBPLAN
, it inherits the limit of its parent subplan APP2_SUBPLAN
, which is 40%. The absolute limit for the consumer group APP2_REPORT_GROUP
is computed as 50% of its parent subplan, which is 50% of 40%, or 20%.
Similarly, because the consumer group APP2_ADHOC_GROUP
is contained in the subplan APP2_REPORTS_SUBPLAN
, its limit is computed as a percentage of its parent subplan. The utilization limit for the consumer group APP2_ADHOC_GROUP
is 50% of 40%, or 20%.
The maximum CPU utilization for the consumer group APP2_OLTP_GROUP
is set to 90%. The parent subplan of APP2_OLTP_GROUP
, APP2_SUBPLAN
, has a limit of 40%. Therefore, the absolute limit for the group APP2_OLTP_GROUP
is 90% of 40%, or 36%.
27.7.3 Example of Using Several Resource Allocation Methods
An example illustrates using several resource allocation methods.
The example presented here could represent a plan for a database supporting a packaged ERP (Enterprise Resource Planning) or CRM (Customer Relationship Management) application. The work in such an environment can be highly varied. There may be a mix of short transactions and quick queries, in combination with longer running batch jobs that include large parallel queries. The goal is to give good response time to OLTP (Online Transaction Processing), while allowing batch jobs to run in parallel.
The plan is summarized in the following table.
Group | CPU Resource Allocation % | Parallel Statement Queuing | Automatic Consumer Group Switching | Maximum Estimated Execution Time | Undo Pool | PGA Limit for Each Session |
---|---|---|---|---|---|---|
|
60% |
-- |
Switch to group: Switch time: 3 secs |
-- |
200K |
20M |
|
30% |
Parallel server limit: 8 Parallel queue timeout: 600 secs |
-- |
3600 secs |
-- |
-- |
|
10% |
-- |
-- |
-- |
-- |
-- |
The following statements create the preceding plan, which is named erp_plan
:
BEGIN DBMS_RESOURCE_MANAGER.CREATE_PENDING_AREA(); DBMS_RESOURCE_MANAGER.CREATE_PLAN(PLAN => 'erp_plan', COMMENT => 'Resource plan/method for ERP Database'); DBMS_RESOURCE_MANAGER.CREATE_CONSUMER_GROUP(CONSUMER_GROUP => 'oltp', COMMENT => 'Resource consumer group/method for OLTP jobs'); DBMS_RESOURCE_MANAGER.CREATE_CONSUMER_GROUP(CONSUMER_GROUP => 'batch', COMMENT => 'Resource consumer group/method for BATCH jobs'); DBMS_RESOURCE_MANAGER.CREATE_PLAN_DIRECTIVE(PLAN => 'erp_plan', GROUP_OR_SUBPLAN => 'oltp', COMMENT => 'OLTP sessions', MGMT_P1 => 60, SWITCH_GROUP => 'batch', SWITCH_TIME => 3, UNDO_POOL => 200, SWITCH_FOR_CALL => TRUE, SESSION_PGA_LIMIT => 20); DBMS_RESOURCE_MANAGER.CREATE_PLAN_DIRECTIVE(PLAN => 'erp_plan', GROUP_OR_SUBPLAN => 'batch', COMMENT => 'BATCH sessions', MGMT_P1 => 30, PARALLEL_SERVER_LIMIT => 8, PARALLEL_QUEUE_TIMEOUT => 600, MAX_EST_EXEC_TIME => 3600); DBMS_RESOURCE_MANAGER.CREATE_PLAN_DIRECTIVE(PLAN => 'erp_plan', GROUP_OR_SUBPLAN => 'OTHER_GROUPS', COMMENT => 'mandatory', MGMT_P1 => 10); DBMS_RESOURCE_MANAGER.VALIDATE_PENDING_AREA(); DBMS_RESOURCE_MANAGER.SUBMIT_PENDING_AREA(); END; /
27.7.4 Example of Managing Parallel Statements Using Directive Attributes
An example illustrates managing parallel statements using directive attributes.
A typical data warehousing environment consists of different types of users with varying resource requirements. Users with common processing needs are grouped into a consumer group. The consumer group URGENT_GROUP
consists of users who run reports that provide important information to top management. This group generates a large number of parallel queries. Users from the consumer group ETL_GROUP
import data from source systems and perform extract, transform, and load (ETL) operations. The group OTHER_GROUPS
contains users who execute ad-hoc queries. You must manage the requirements of these diverse groups of users while optimizing performance.
You can use the following directive attributes to manage and optimize the execution of parallel statements:
-
MGMT_P
n -
PARALLEL_SERVER_LIMIT
-
PARALLEL_STMT_CRITICAL
-
PARALLEL_QUEUE_TIMEOUT
-
PQ_TIMEOUT_ACTION
-
PARALLEL_DEGREE_LIMIT_P1
-
SHARES
Note:
-
The
MGMT_P
n management attributes andSHARES
attribute control how a parallel statement is selected from the parallel statement queue for execution. You can prioritize the parallel statements of one consumer group over another by setting a higher value for the management attributes of that group. -
In a multitenant environment, if you want more per-workload management, then you can use the
SHARES
attribute to specify the share of resource allocation for pluggable databases (PDBs), which includes the parallel statement queuing resource. Alternatively, you can use the other directive attributes mentioned above.
Table 27-4 describes the resource allocations of the plan DW_PLAN
, which can be used to manage the needs of the data warehouse users. This plan contains the consumer groups URGENT_GROUP
, ETL_GROUP
, and OTHER_GROUPS
. This example demonstrates the use of directive attributes in ensuring that one application or consumer group does not use all the available parallel execution servers.
Table 27-4 Resource Plan with Parallel Statement Directives
Consumer Group | Level 1 CPU Allocation | Level 2 CPU Allocation | Level 3 CPU Allocation | PARALLEL_DEGREE_LIMIT_P1 | PARALLEL_SERVER_LIMIT | PARALLEL_QUEUE_TIMEOUT |
---|---|---|---|---|---|---|
|
100% |
12 |
||||
|
100% |
8 |
50% |
|||
|
100% |
2 |
50% |
360 |
In this example, the parameter PARALLEL_SERVERS_TARGET
initialization parameter is set to 64, which means that the number of parallel execution servers available is 64. The total number of parallel execution servers that can be used for parallel statement execution before URGENT_GROUP
sessions with PARALLEL_DEGREE_POLICY
set to AUTO
are added to the parallel statement queue is equal to 64. Because the PARALLEL_SERVER_LIMIT
attribute of ETL_GROUP
and OTHER_GROUPS
is 50%, the maximum number of parallel execution servers that can be used by these groups is 50% of 64, or 32 parallel execution servers each.
Note that parallel statements from a consumer group will only be queued if the PARALLEL_DEGREE_POLICY
parameter is set to AUTO
and the total number of active servers for the consumer group is higher than PARALLEL_SERVERS_TARGET
. If PARALLEL_DEGREE_POLICY
is set to MANUAL
or LIMITED
, then the statements are run provided there are enough parallel execution servers available. The parallel execution servers used by such a statement will count toward the total number of parallel execution servers used by the consumer group. However, the parallel statement will not be added to the parallel statement queue.
Tip:
For low-priority applications, it is a common practice to set low values for PARALLEL_DEGREE_LIMIT_P1
and PARALLEL_SERVER_LIMIT
.
Because URGENT_GROUP
has 100% of the allocation at level 1, its parallel statements will always be dequeued ahead of the other consumer groups from the parallel statement queue. Although URGENT_GROUP
has no PARALLEL_SERVER_LIMIT
directive attribute, a statement issued by a session in this group might still be queued if there are not enough available parallel execution servers to run it.
When you create the resource plan directive for the URGENT_GROUP
, you can set the PARALLEL_STMT_CRITICAL
parameter to BYPASS_QUEUE
. With this setting, parallel statements from the consumer group bypass the parallel statements queue and are executed immediately. However, the number of parallel execution servers might exceed the setting of the PARALLEL_SERVERS_TARGET
initialization parameter, and the degree of parallelism might be lower if the limit set by the PARALLEL_MAX_SERVERS
initialization parameter is reached.
The degree of parallelism, represented by PARALLEL_DEGREE_LIMIT_P1
, is set to 12 for URGENT_GROUP
. Therefore, each parallel statement from URGENT_GROUP
can use a maximum of 12 parallel execution servers. Similarly, each parallel statement from the ETL_GROUP
can use a maximum of 8 parallel execution servers and each parallel statement from the OTHER_GROUPS
can use 2 parallel execution servers.
Suppose, at a given time, the only parallel statements are from the ETL_GROUP
, and they are using 26 out of the 32 parallel execution servers available to this group. Sessions from this consumer group have PARALLEL_DEGREE_POLICY
set to AUTO
. If another parallel statement with the PARALLEL_DEGREE_LIMIT_P1
attribute set to 8 is launched from ETL_GROUP
, then this query cannot be run immediately because the available parallel execution servers in the ETL_GROUP
is 32-26=6 parallel execution servers. The new parallel statement is queued until the number of parallel execution servers it requires is available in ETL_GROUP
.
While the parallel statements in ETL_GROUP
are being executed, suppose a parallel statement is launched from OTHER_GROUPS
. This group still has 32 parallel execution servers available and so the parallel statement is executed.
The PARALLEL_QUEUE_TIMEOUT
attribute for OTHER_GROUPS
is set to 360. Therefore, any parallel statement from this group can remain in the parallel execution server queue for 360 seconds only. After this time, the parallel statement is removed from the queue and the error ORA-07454
is returned.
27.7.5 An Oracle-Supplied Mixed Workload Plan
Oracle Database includes a predefined resource plan, MIXED_WORKLOAD_PLAN
, that prioritizes interactive operations over batch operations, and includes the required subplans and consumer groups recommended by Oracle.
MIXED_WORKLOAD_PLAN
is defined as follows:
Group or Subplan | CPU Resource Allocation | ||||
---|---|---|---|---|---|
Level 1 | Level 2 | Level 3 | Automatic Consumer Group Switching | Max Degree of Parallelism | |
|
100% |
||||
|
85% |
Switch to group: Switch time: 60 seconds Switch for call: |
1 |
||
|
5% |
||||
|
5% |
||||
|
100% |
In this plan, because INTERACTIVE_GROUP
is intended for short transactions, any call that consumes more than 60 seconds of CPU time is automatically switched to BATCH_GROUP
, which is intended for longer batch operations.
You can use this predefined plan if it is appropriate for your environment. (You can modify the plan, or delete it if you do not intend to use it.) Note that there is nothing special about the names BATCH_GROUP
and INTERACTIVE_GROUP
. The names reflect only the intended purposes of the groups, and it is up to you to map application sessions to these groups and adjust CPU resource allocation percentages accordingly so that you achieve proper resource management for your interactive and batch applications. For example, to ensure that your interactive applications run under the INTERACTIVE_GROUP
consumer group, you must map your interactive applications' user sessions to this consumer group based on user name, service name, program name, module name, or action, as described in "Specifying Session-to-Consumer Group Mapping Rules". You must map your batch applications to the BATCH_GROUP
in the same way. Finally, you must enable this plan as described in "Enabling Oracle Database Resource Manager and Switching Plans".
See Table 27-5 and Table 27-6 for explanations of the other resource consumer groups and subplans in this plan.
27.8 Managing Multiple Database Instances on a Single Server
Oracle Database provides a method for managing CPU allocations on a multi-CPU server running multiple database instances. This method is called instance caging. Instance caging and Oracle Database Resource Manager (the Resource Manager) work together to support desired levels of service across multiple instances.
- About Instance Caging
A simple way to limit CPU consumption for each database instance is to use instance caging. Instance caging is a method that uses an initialization parameter to limit the number of CPUs that an instance can use simultaneously. - Enabling Instance Caging
You can enable instance caging using by creating a resource plan with CPU directives and setting theCPU_COUNT
initialization parameter.
Parent topic: Managing Resources with Oracle Database Resource Manager
27.8.1 About Instance Caging
A simple way to limit CPU consumption for each database instance is to use instance caging. Instance caging is a method that uses an initialization parameter to limit the number of CPUs that an instance can use simultaneously.
You might decide to run multiple Oracle database instances on a single multi-CPU server. A typical reason to do so would be server consolidation—using available hardware resources more efficiently. When running multiple instances on a single server, the instances compete for CPU. One resource-intensive database instance could significantly degrade the performance of the other instances. For example, on a 16-CPU system with four database instances, the operating system might be running one database instance on the majority of the CPUs during a period of heavy load for that instance. This could degrade performance in the other three instances. CPU allocation decisions such as this are made solely by the operating system; the user generally has no control over them.
In the previous example, if you use instance caging to limit the number of CPUs to four for each of the four instances, there is less likelihood that one instance can interfere with the others. When constrained to four CPUs, an instance might become CPU-bound. This is when the Resource Manager begins to do its work to allocate CPU among the various database sessions according to the resource plan that you set for the instance. Thus, instance caging and the Resource Manager together provide a simple, effective way to manage multiple instances on a single server.
There are two typical approaches to instance caging for a server:
-
Over-subscribing—You would use this approach for non-critical databases such as development and test systems, or low-load non-critical production systems. In this approach, the sum of the CPU limits for each instance exceeds the actual number of CPUs on the system. For example, on a 4-CPU system with four database instances, you might limit each instance to three CPUs. When a server is over-subscribed in this way, the instances can impact each other's performance. However, instance caging limits the impact and helps provide somewhat predictable performance. However, if one of the instances has a period of high load, the CPUs are available to handle it. This is a reasonable approach for non-critical systems, because one or more of the instances may frequently be idle or at a very low load.
-
Partitioning—This approach is for critical production systems, where you want to prevent instances from interfering with each other. You allocate CPUs such that the sum of all allocations is equal to the number of CPUs on the server. For example, on a 16-server system, you might allocate 8 CPUs to the first instance, 4 CPUs to the second, and 2 each to the remaining two instances. By dedicating CPU resources to each database instance, the load on one instance cannot affect another's, and each instance performs predictably.
Using Instance Caging with Utilization Limit
If you enable instance caging and set a utilization limit in your resource plan, then the absolute limit is computed as a percentage of the allocated CPU resources.
For example, if you enable instance caging and set the CPU_COUNT
to 4, and a consumer group has a utilization limit of 50%, then the consumer group can use a maximum of 50% of 4 CPUs, which is 2 CPUs.
Parent topic: Managing Multiple Database Instances on a Single Server
27.8.2 Enabling Instance Caging
You can enable instance caging using by creating a resource plan with CPU directives and setting the CPU_COUNT
initialization parameter.
To enable instance caging, do the following for each instance on the server:
Parent topic: Managing Multiple Database Instances on a Single Server
27.9 Maintaining Consumer Groups, Plans, and Directives
You can maintain consumer groups, resource plans, and resource plan directives for Oracle Database Resource Manager (the Resource Manager). You perform maintenance tasks using the DBMS_RESOURCE_MANAGER
PL/SQL package.
- Updating a Consumer Group
You use theUPDATE_CONSUMER_GROUP
procedure to update consumer group information. - Deleting a Consumer Group
TheDELETE_CONSUMER_GROUP
procedure deletes the specified consumer group. - Updating a Plan
You use theUPDATE_PLAN
procedure to update plan information. - Deleting a Plan
TheDELETE_PLAN
procedure deletes the specified plan as well as all the plan directives associated with it. - Updating a Resource Plan Directive
Use theUPDATE_PLAN_DIRECTIVE
procedure to update plan directives. - Deleting a Resource Plan Directive
To delete a resource plan directive, use theDELETE_PLAN_DIRECTIVE
procedure.
See Also:
-
Oracle Database PL/SQL Packages and Types Reference for details on the
DBMS_RESOURCE_MANAGER
PL/SQL package.
Parent topic: Managing Resources with Oracle Database Resource Manager
27.9.1 Updating a Consumer Group
You use the UPDATE_CONSUMER_GROUP
procedure to update consumer group information.
To update a consumer group:
-
Create a pending area.
-
Run the
UPDATE_CONSUMER_GROUP
procedure .If you do not specify the arguments for the
UPDATE_CONSUMER_GROUP
procedure, then they remain unchanged in the data dictionary. -
Submit the pending area.
Related Topics
Parent topic: Maintaining Consumer Groups, Plans, and Directives
27.9.2 Deleting a Consumer Group
The DELETE_CONSUMER_GROUP
procedure deletes the specified consumer group.
To delete a consumer group:
-
Create a pending area.
-
Run the
DELETE_CONSUMER_GROUP
procedure . -
Submit the pending area.
Upon deletion of a consumer group, all users having the deleted group as their initial consumer group are assigned the OTHER_GROUPS
as their initial consumer group. All currently running sessions belonging to a deleted consumer group are assigned to a new consumer group, based on the consumer group mapping rules. If no consumer group is found for a session through mapping, the session is switched to the OTHER_GROUPS
.
You cannot delete a consumer group if it is referenced by a resource plan directive.
Related Topics
Parent topic: Maintaining Consumer Groups, Plans, and Directives
27.9.3 Updating a Plan
You use the UPDATE_PLAN
procedure to update plan information.
To update a plan:
-
Create a pending area.
-
Run the
UPDATE_PLAN
procedure. For example, the following PL/SQL block updates theCOMMENT
parameter:BEGIN DBMS_RESOURCE_MANAGER.UPDATE_PLAN( PLAN => 'DAYTIME', NEW_COMMENT => '50% more resources for OLTP applications'); END; /
If you do not specify the arguments for the
UPDATE_PLAN
procedure, they remain unchanged in the data dictionary. -
Submit the pending area.
Related Topics
Parent topic: Maintaining Consumer Groups, Plans, and Directives
27.9.4 Deleting a Plan
The DELETE_PLAN
procedure deletes the specified plan as well as all the plan directives associated with it.
To delete a plan:
-
Create a pending area.
-
Run the
DELETE_PLAN_CASCADE
procedure. For example, the following PL/SQL block deletes thegreat_bread
plan and its directives.BEGIN DBMS_RESOURCE_MANAGER.DELETE_PLAN(PLAN => 'great_bread'); END; /
If you do not specify the arguments for the
UPDATE_PLAN
procedure, they remain unchanged in the data dictionary.The resource consumer groups referenced by the deleted directives are not deleted, but they are no longer associated with the
great_bread
plan.The
DELETE_PLAN_CASCADE
procedure deletes the specified plan as well as all its descendants: plan directives and those subplans and resource consumer groups that are not marked by the database as mandatory. IfDELETE_PLAN_CASCADE
encounters an error, then it rolls back, leaving the plan unchanged.You cannot delete the currently active plan.
-
Submit the pending area.
Related Topics
Parent topic: Maintaining Consumer Groups, Plans, and Directives
27.9.5 Updating a Resource Plan Directive
Use the UPDATE_PLAN_DIRECTIVE
procedure to update plan directives.
To update a resource plan directive:
-
Create a pending area.
-
Run the
UPDATE_PLAN_DIRECTIVE
procedure.The following example adds a comment to a directive:
BEGIN DBMS_RESOURCE_MANAGER.CLEAR_PENDING_AREA(); DBMS_RESOURCE_MANAGER.CREATE_PENDING_AREA(); DBMS_RESOURCE_MANAGER.UPDATE_PLAN_DIRECTIVE( PLAN => 'SIMPLE_PLAN1', GROUP_OR_SUBPLAN => 'MYGROUP1', NEW_COMMENT => 'Higher priority' ); DBMS_RESOURCE_MANAGER.SUBMIT_PENDING_AREA(); END; /
To clear (nullify) a comment, pass a null string (
''
). To clear (zero or nullify) any numeric directive parameter, set its new value to -1:BEGIN DBMS_RESOURCE_MANAGER.CLEAR_PENDING_AREA(); DBMS_RESOURCE_MANAGER.CREATE_PENDING_AREA(); DBMS_RESOURCE_MANAGER.UPDATE_PLAN_DIRECTIVE( PLAN => 'SIMPLE_PLAN1', GROUP_OR_SUBPLAN => 'MYGROUP1', NEW_MAX_EST_EXEC_TIME => -1 ); DBMS_RESOURCE_MANAGER.SUBMIT_PENDING_AREA(); END; /
If you do not specify an argument for the
UPDATE_PLAN_DIRECTIVE
procedure, then its corresponding parameter in the directive remains unchanged. -
Submit the pending area.
Related Topics
Parent topic: Maintaining Consumer Groups, Plans, and Directives
27.9.6 Deleting a Resource Plan Directive
To delete a resource plan directive, use the DELETE_PLAN_DIRECTIVE
procedure.
To delete a resource plan directive:
-
Create a pending area.
-
Run the
DELETE_PLAN_DIRECTIVE
procedure. -
Submit the pending area.
Related Topics
Parent topic: Maintaining Consumer Groups, Plans, and Directives
27.10 Viewing Database Resource Manager Configuration and Status
You can use several static data dictionary views and dynamic performance views to view the current configuration and status of Oracle Database Resource Manager (the Resource Manager).
- Viewing Consumer Groups Granted to Users or Roles
TheDBA_RSRC_CONSUMER_GROUP_PRIVS
view displays the consumer groups granted to users or roles. - Viewing Plan Information
An example illustrates using theDBA_RSRC_PLANS
view to display all of the resource plans defined in the database. - Viewing Current Consumer Groups for Sessions
You can use theV$SESSION
view to display the consumer groups that are currently assigned to sessions. - Viewing the Currently Active Plans
TheV$RSRC_PLAN
view displays currently active plans.
See Also:
Oracle Database Reference for details on all static data dictionary views and dynamic performance views
Parent topic: Managing Resources with Oracle Database Resource Manager
27.10.1 Viewing Consumer Groups Granted to Users or Roles
The DBA_RSRC_CONSUMER_GROUP_PRIVS
view displays the consumer groups granted to users or roles.
Specifically, it displays the groups to which a user or role is allowed to belong or be switched. For example, in the view shown below, user SCOTT
always starts in the SALES
consumer group, can switch to the MARKETING
group through a specific grant, and can switch to the DEFAULT_CONSUMER_GROUP
(OTHER_GROUPS
) and LOW_GROUP
groups because they are granted to PUBLIC
. SCOTT
also can grant the SALES
group but not the MARKETING
group to other users.
SELECT * FROM dba_rsrc_consumer_group_privs; GRANTEE GRANTED_GROUP GRANT_OPTION INITIAL_GROUP ------------------ ------------------------------ ------------ ------------- PUBLIC DEFAULT_CONSUMER_GROUP YES YES PUBLIC LOW_GROUP NO NO SCOTT MARKETING NO NO SCOTT SALES YES YES SYSTEM SYS_GROUP NO YES
SCOTT
was granted the ability to switch to these groups using the DBMS_RESOURCE_MANAGER_PRIVS
package.
27.10.2 Viewing Plan Information
An example illustrates using the DBA_RSRC_PLANS
view to display all of the resource plans defined in the database.
All plans have a NULL
status, meaning that they are not in the pending area.
Note:
Plans in the pending area have a status of PENDING
. Plans in the pending area are being edited.
SELECT plan,status,comments FROM dba_rsrc_plans; PLAN STATUS COMMENTS --------------------------- -------- ---------------------------------------- DSS_PLAN Example plan for DSS workloads that prio... ETL_CRITICAL_PLAN Example plan for DSS workloads that prio... MIXED_WORKLOAD_PLAN Example plan for a mixed workload that p... DEFAULT_MAINTENANCE_PLAN Default plan for maintenance windows tha... DEFAULT_PLAN Default, basic, pre-defined plan that pr... INTERNAL_QUIESCE Plan for quiescing the database. This p... INTERNAL_PLAN Internally-used plan for disabling the r... . . .
27.10.3 Viewing Current Consumer Groups for Sessions
You can use the V$SESSION
view to display the consumer groups that are currently assigned to sessions.
The following example queries the V$SESSION
view:
SELECT sid,serial#,username,resource_consumer_group FROM v$session; SID SERIAL# USERNAME RESOURCE_CONSUMER_GROUP ----- ------- ------------------------ -------------------------------- 11 136 SYS SYS_GROUP 13 16570 SCOTT SALES ...
27.10.4 Viewing the Currently Active Plans
The V$RSRC_PLAN
view displays currently active plans.
This example sets mydb_plan
, as created by the example shown in "Multilevel Plan Example", as the top level plan. It then queries the V$RSRC_PLAN
view to display the currently active plans. The view displays the current top level plan and all of its descendent subplans.
ALTER SYSTEM SET RESOURCE_MANAGER_PLAN = mydb_plan; System altered. SELECT name, is_top_plan FROM v$rsrc_plan; NAME IS_TOP_PLAN ---------------------------- MYDB_PLAN TRUE MAILDB_PLAN FALSE BUGDB_PLAN FALSE
27.11 Monitoring Oracle Database Resource Manager
A set of dynamic performance views enable you to monitor the results of your Oracle Database Resource Manager settings.
Use the following dynamic performance views to help you monitor the results of your Oracle Database Resource Manager settings:
These views provide:
-
Current status information
-
History of resource plan activations
-
Current and historical statistics on resource consumption and CPU waits by both resource consumer group and session
In addition, historical statistics are available through the DBA_HIST_RSRC_PLAN
and DBA_HIST_RSRC_CONSUMER_GROUP
views, which contain Automatic Workload Repository (AWR) snapshots of the V$RSRC_PLAN_HISTORY
and V$RSRC_CONS_GROUP_HISTORY
, respectively.
For assistance with tuning, the views V$RSRCMGRMETRIC
and V$RSRCMGRMETRIC_HISTORY
show how much time was spent waiting for CPU and how much CPU was consumed per minute for every consumer group for the past hour. These metrics can also be viewed graphically with Cloud Control, on the Resource Manager Statistics page.
When Resource Manager is enabled, Resource Manager automatically records statistics about resource usage, and you can examine these statistics using real-time SQL monitoring and Resource Manager dynamic performance views.
You can use real-time SQL monitoring by accessing the SQL Monitor page in Cloud Control or by querying the V$SQL_MONITOR
view and other related views. The V$SQL_MONITOR
view also includes information about the last action performed by Resource Manager for a consumer group in the following columns: RM_CONSUMER_GROUP
, RM_LAST_ACTION
, RM_LAST_ACTION_REASON
, and RM_LAST_ACTION_TIME
.
In addition, the following dynamic performance views contain statistics about resource usage:
-
V$RSRCMGRMETRIC
-
V$RSRCMGRMETRIC_HISTORY
-
V$RSRC_CONSUMER_GROUP
-
V$RSRC_CONS_GROUP_HISTORY
See Also:
Oracle Database SQL Tuning Guide for more information about real-time SQL monitoring
V$RSRC_PLAN
This view displays the currently active resource plan and its subplans.
SELECT name, is_top_plan FROM v$rsrc_plan; NAME IS_TOP_PLAN -------------------------------- ----------- DEFAULT_PLAN TRUE ORA$AUTOTASK FALSE ORA$AUTOTASK_HIGH_SUB_PLAN FALSE
The plan for which IS_TOP_PLAN
is TRUE
is the currently active (top) plan, and the other plans are subplans of either the top plan or of other subplans in the list.
This view also contains other information, including the following:
-
The
INSTANCE_CAGING
column shows whether instance caging is enabled. -
The
CPU_MANAGED
column shows whether CPU is being managed. -
The
PARALLEL_EXECUTION_MANAGED
column shows whether parallel statement queuing is enabled.
See Also:
V$RSRC_CONSUMER_GROUP
Use the V$RSRC_CONSUMER_GROUP
view to monitor resources consumed, including CPU, I/O, and parallel execution servers. It can also be used to monitor statistics related to CPU resource management, runaway query management, parallel statement queuing, and so on. All of the statistics are cumulative from the time when the plan was activated.
SELECT name, active_sessions, queue_length, consumed_cpu_time, cpu_waits, cpu_wait_time FROM v$rsrc_consumer_group; NAME ACTIVE_SESSIONS QUEUE_LENGTH CONSUMED_CPU_TIME CPU_WAITS CPU_WAIT_TIME ------------------ --------------- ------------ ----------------- ---------- ------------- OLTP_ORDER_ENTRY 1 0 29690 467 6709 OTHER_GROUPS 0 0 5982366 4089 60425 SYS_GROUP 1 0 2420704 914 19540 DSS_QUERIES 4 2 4594660 3004 55700
In the preceding query results, the DSS_QUERIES
consumer group has four sessions in its active session pool and two more sessions queued for activation.
A key measure in this view is CPU_WAIT_TIME
. This indicates the total time that sessions in the consumer group waited for CPU because of resource management. Not included in this measure are waits due to latch or enqueue contention, I/O waits, and so on.
Note:
The V$RSRC_CONSUMER_GROUP
view records statistics for resources that are not currently being managed by Resource Manager. when the STATISTICS_LEVEL
initialization parameter is set to ALL
or TYPICAL
.
See Also:
V$RSRC_SESSION_INFO
Use this view to monitor the status of one or more sessions. The view shows how the session has been affected by the Resource Manager. It provides information such as:
-
The consumer group that the session currently belongs to.
-
The consumer group that the session originally belonged to.
-
The session attribute that was used to map the session to the consumer group.
-
Session state (
RUNNING
,WAIT_FOR_CPU
,QUEUED
, and so on). -
Current and cumulative statistics for metrics, such as CPU consumed, wait times, queued time, and number of active parallel servers used. Current statistics reflect statistics for the session since it joined its current consumer group. Cumulative statistics reflect statistics for the session in all consumer groups to which it has belonged since it was created.
SELECT se.sid sess_id, co.name consumer_group, se.state, se.consumed_cpu_time cpu_time, se.cpu_wait_time, se.queued_time FROM v$rsrc_session_info se, v$rsrc_consumer_group co WHERE se.current_consumer_group_id = co.id; SESS_ID CONSUMER_GROUP STATE CPU_TIME CPU_WAIT_TIME QUEUED_TIME ------- ------------------ -------- --------- ------------- ----------- 113 OLTP_ORDER_ENTRY WAITING 137947 28846 0 135 OTHER_GROUPS IDLE 785669 11126 0 124 OTHER_GROUPS WAITING 50401 14326 0 114 SYS_GROUP RUNNING 495 0 0 102 SYS_GROUP IDLE 88054 80 0 147 DSS_QUERIES WAITING 460910 512154 0
CPU_WAIT_TIME
in this view has the same meaning as in the V$RSRC_CONSUMER_GROUP
view, but applied to an individual session.
You can join this view with the V$SESSION
view for more information about a session.
V$RSRC_PLAN_HISTORY
This view shows when resource plans were enabled or disabled on the instance. Each resource plan activation or deactivation is assigned a sequence number. For each entry in the view, the V$RSRC_CONS_GROUP_HISTORY
view has a corresponding entry for each consumer group in the plan that shows the cumulative statistics for the consumer group. The two views are joined by the SEQUENCE#
column in each.
SELECT sequence# seq, name plan_name, to_char(start_time, 'DD-MON-YY HH24:MM') start_time, to_char(end_time, 'DD-MON-YY HH24:MM') end_time, window_name FROM v$rsrc_plan_history; SEQ PLAN_NAME START_TIME END_TIME WINDOW_NAME ---- -------------------------- --------------- --------------- ---------------- 1 29-MAY-07 23:05 29-MAY-07 23:05 2 DEFAULT_MAINTENANCE_PLAN 29-MAY-07 23:05 30-MAY-07 02:05 TUESDAY_WINDOW 3 30-MAY-07 02:05 30-MAY-07 22:05 4 DEFAULT_MAINTENANCE_PLAN 30-MAY-07 22:05 31-MAY-07 02:05 WEDNESDAY_WINDOW 5 31-MAY-07 02:05 31-MAY-07 22:05 6 DEFAULT_MAINTENANCE_PLAN 31-MAY-07 22:05 THURSDAY_WINDOW
A null value under PLAN_NAME
indicates that no plan was active.
AWR snapshots of this view are stored in the DBA_HIST_RSRC_PLAN
view.
See Also:
V$RSRC_CONS_GROUP_HISTORY
This view helps you understand how resources were shared among the consumer groups over time. The sequence#
column corresponds to the column of the same name in the V$RSRC_PLAN_HISTORY
view. Therefore, you can determine the plan that was active for each row of consumer group statistics.
SELECT sequence# seq, name, cpu_wait_time, cpu_waits, consumed_cpu_time FROM v$rsrc_cons_group_history; SEQ NAME CPU_WAIT_TIME CPU_WAITS CONSUMED_CPU_TIME ---- ------------------------- ------------- ---------- ----------------- 2 SYS_GROUP 18133 691 33364431 2 OTHER_GROUPS 51252 825 181058333 2 ORA$AUTOTASK_MEDIUM_GROUP 21 5 4019709 2 ORA$AUTOTASK_URGENT_GROUP 35 1 198760 2 ORA$AUTOTASK_STATS_GROUP 0 0 0 2 ORA$AUTOTASK_SPACE_GROUP 0 0 0 2 ORA$AUTOTASK_SQL_GROUP 0 0 0 2 ORA$AUTOTASK_HEALTH_GROUP 0 0 0 4 SYS_GROUP 40344 85 42519265 4 OTHER_GROUPS 123295 1040 371481422 4 ORA$AUTOTASK_MEDIUM_GROUP 1 4 7433002 4 ORA$AUTOTASK_URGENT_GROUP 22959 158 19964703 4 ORA$AUTOTASK_STATS_GROUP 0 0 0 . .
AWR snapshots of this view are stored in the DBA_HIST_RSRC_CONSUMER_GROUP
view. Use DBA_HIST_RSRC_CONSUMER_GROUP
with DBA_HIST_RSRC_PLAN
to determine the plan that was active for each historical set of consumer group statistics.
Note:
The V$RSRC_CONS_GROUP_HISTORY
view records statistics for resources that are not currently being managed by Resource Manager. when the STATISTICS_LEVEL
initialization parameter is set to ALL
or TYPICAL
.
See Also:
-
Oracle Database Performance Tuning Guide for information about the AWR.
V$RSRCMGRMETRIC
This view enables you to track CPU metrics in milliseconds, in terms of number of sessions, or in terms of utilization for the past one minute. It provides real-time metrics for each consumer group and is very useful in scenarios where you are running workloads and want to continuously monitor CPU resource utilization.
Use this view to compare the maximum possible CPU utilization and average CPU utilization percentage for consumer groups with other consumer group settings such as CPU time used, time waiting for CPU, average number of sessions that are consuming CPU, and number of sessions that are waiting for CPU allocation. For example, you can view the amount of CPU resources a consumer group used and how long it waited for resource allocation. Or, you can view how many sessions from each consumer group are executed against the total number of active sessions.
To track CPU consumption in terms of CPU utilization, use the CPU_UTILIZATION_LIMIT
and AVG_CPU_UTILIZATION
columns. AVG_CPU_UTILIZATION
lists the average percentage of the server's CPU that is consumed by a consumer group. CPU_UTILIZATION_LIMIT
represents the maximum percentage of the server's CPU that a consumer group can use. This limit is set using the UTILIZATION_LIMIT
directive attribute.
SELECT consumer_group_name, cpu_utilization_limit, avg_cpu_utilization FROM v$rsrcmgrmetric;
Use the CPU_CONSUMED_TIME
and CPU_TIME_WAIT
columns to track CPU consumption and throttling in milliseconds. The column NUM_CPUS
represents the number of CPUs that Resource Manager is managing.
SELECT consumer_group_name, cpu_consumed_time, cpu_wait_time, num_cpus FROM v$rsrcmgrmetric;
To track the CPU consumption and throttling in terms of number of sessions, use the RUNNING_SESSIONS_LIMIT
, AVG_RUNNING_SESSIONS
, and AVG_WAITING_SESSIONS
columns. RUNNING_SESSIONS_LIMIT
lists the maximum number of sessions, from a particular consumer group, that can be running at any time. This limit is defined by the UTILIZATION_LIMIT
directive attribute that you set either for the consumer group or for a subplan that contains the consumer group. For each consumer group, AVG_RUNNING_SESSIONS
lists the average number of sessions that are consuming CPU and AVG_WAITING_SESSIONS
lists the average number of sessions that are waiting for CPU.
SELECT sequence#, consumer_group_name, running_sessions_limit, avg_running_sessions, avg_waiting_sessions FROM v$rsrcmgrmetric;
To track parallel statements and parallel server use for a consumer group, use the AVG_ACTIVE_PARALLEL_STMTS
, AVG_QUEUED_PARALLEL_STMTS
, AVG_ACTIVE_PARALLEL_SERVERS
, AVG_QUEUED_PARALLEL_SERVERS
, and PARALLEL_SERVERS_LIMIT
columns. AVG_ACTIVE_PARALLEL_STMTS
and AVG_ACTIVE_PARALLEL_SERVERS
list the average number of parallel statements running and the average number of parallel servers used by the parallel statements. AVG_QUEUED_PARALLEL_STMTS
and AVG_QUEUED_PARALLEL_SERVERS
list the average number of parallel statements queued and average number of parallel servers that were requested by queued parallel statements. PARALLEL_SERVERS_LIMIT
lists the number of parallel servers allowed to be used by the consumer group.
SELECT avg_active_parallel_stmts, avg_queued_parallel_stmts, avg_active_parallel_servers, avg_queued_parallel_servers, parallel_servers_limit FROM v$rsrcmgrmetric;
Note:
The V$RSRCMGRMETRIC
view records statistics for resources that are not currently being managed by Resource Manager. when the STATISTICS_LEVEL
initialization parameter is set to ALL
or TYPICAL
.
See Also:
V$RSRCMGRMETRIC_HISTORY
The columns in the V$RSRCMGRMETRIC_HISTORY
are the same view as V$RSRCMGRMETRIC. The only difference between these views is that V$RSRCMGRMETRIC contains metrics for the past one minute only, whereas V$RSRCMGRMETRIC_HISTORY
contains metrics for the last 60 minutes.
Note:
The V$RSRCMGRMETRIC_HISTORY
view records statistics for resources that are not currently being managed by Resource Manager. when the STATISTICS_LEVEL
initialization parameter is set to ALL
or TYPICAL
.
See Also:
Parent topic: Managing Resources with Oracle Database Resource Manager
27.12 Interacting with Operating-System Resource Control
Many operating systems provide tools for resource management. These tools often contain "workload manager" or "resource manager" in their names, and are intended to allow multiple applications to share the resources of a single server, using an administrator-defined policy. Examples are Hewlett Packard's Process Resource Manager or Solaris Containers, Zones, and Resource Pools.
- Guidelines for Using Operating-System Resource Control
Follow guidelines if you use operating-system resource control.
Parent topic: Managing Resources with Oracle Database Resource Manager
27.12.1 Guidelines for Using Operating-System Resource Control
Follow guidelines if you use operating-system resource control.
If you choose to use operating-system resource control with Oracle Database, then you must use it judiciously, according to the following guidelines:
-
If you have multiple instances on a node, and you want to distribute resources among them, then each instance should be assigned to a dedicated operating-system resource manager group or managed entity. To run multiple instances in the managed entity, use instance caging to manage how the CPU resources within the managed entity should be distributed among the instances. When Oracle Database Resource Manager is managing CPU resources, it expects a fixed amount of CPU resources for the instance. Without instance caging, it expects the available CPU resources to be equal to the number of CPUs in the managed entity. With instance caging, it expects the available CPU resources to be equal to the value of the
CPU_COUNT
initialization parameter. If there are less CPU resources than expected, then the Oracle Database Resource Manager is not as effective at enforcing the resource allocations in the resource plan. See "Managing Multiple Database Instances on a Single Server" for information about instance caging. -
The dedicated entity running all the instance's processes must run at one priority (or resource consumption) level.
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The CPU resources assigned to the dedicated entity cannot be changed more frequently than once every few minutes.
If the operating-system resource manager is rapidly changing the CPU resources allocated to an Oracle instance, then the Oracle Database Resource Manager might not manage CPU resources effectively. In particular, if the CPU resources allocated to the Oracle instance changes more frequently than every couple of minutes, then these changes might not be observed by Oracle because it only checks for such changes every couple of minutes. In these cases, Oracle Database Resource Manager can over-schedule processes if it concludes that more CPU resources are available than there actually are, and it can under-schedule processes if it concludes that less CPU resources are available than there actually are. If it over-schedules processes, then the
UTILIZATION_LIMIT
directives might be exceeded, and the CPU directives might not be accurately enforced. If it under-schedules processes, then the Oracle instance might not fully use the server's resources. -
Process priority management must not be enabled.
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Management of individual database processes at different priority levels (for example, using the
nice
command on UNIX platforms) is not supported. Severe consequences, including instance crashes, can result. Similar undesirable results are possible if operating-system resource control is permitted to manage the memory to which an Oracle Database instance is pinned.
Parent topic: Interacting with Operating-System Resource Control
27.13 Oracle Database Resource Manager Reference
Resource Manager includes predefined resource plans, consumer groups, and consumer groups mapping rules. You can query data dictionary views for information about your Resource Manager configuration.
- Predefined Resource Plans and Consumer Groups
Oracle Database includes predefined resource plans. - Predefined Consumer Group Mapping Rules
Oracle Database includes predefined consumer group mapping rules. - Resource Manager Data Dictionary Views
You can query a set of data dictionary views for information relating to database resource management.
Parent topic: Managing Resources with Oracle Database Resource Manager
27.13.1 Predefined Resource Plans and Consumer Groups
Oracle Database includes predefined resource plans.
Table 27-5 lists the resource plans and Table 27-6 lists the resource consumer groups that are predefined in each Oracle database. You can verify these by querying the views DBA_RSRC_PLANS
and DBA_RSRC_CONSUMER_GROUPS
.
The following query displays the CPU allocations in the example plan DSS_PLAN
:
SELECT group_or_subplan, mgmt_p1, mgmt_p2, mgmt_p3, mgmt_p4 FROM dba_rsrc_plan_directives WHERE plan = 'DSS_PLAN'; GROUP_OR_SUBPLAN MGMT_P1 MGMT_P2 MGMT_P3 MGMT_P4 ------------------------------ ---------- ---------- ---------- ---------- SYS_GROUP 75 0 0 0 DSS_CRITICAL_GROUP 18 0 0 0 DSS_GROUP 3 0 0 0 ETL_GROUP 1 0 0 0 BATCH_GROUP 1 0 0 0 ORA$AUTOTASK 1 0 0 0 OTHER_GROUPS 1 0 0 0
Table 27-5 Predefined Resource Plans
Resource Plan | Description |
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Default plan for maintenance windows. See "About Resource Allocations for Automated Maintenance Tasks" for details of this plan. Because maintenance windows are regular Oracle Scheduler windows, you can change the resource plan associated with them, if desired. If you do change a maintenance window resource plan, ensure that you include the subplan |
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Basic default plan that prioritizes |
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Example plan for a data warehouse that prioritizes critical DSS queries over non-critical DSS queries and ETL operations. |
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Example plan for a data warehouse that prioritizes ETL operations over DSS queries. |
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For disabling the resource manager. For internal use only. |
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For quiescing the database. This plan cannot be activated directly. To activate, use the |
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Example plan for a mixed workload that prioritizes interactive operations over batch operations. See "An Oracle-Supplied Mixed Workload Plan" for details. |
Table 27-6 Predefined Resource Consumer Groups
Resource Consumer Group | Description |
---|---|
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Consumer group for batch operations. Referenced by the example plan |
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Consumer group for critical DSS queries. Referenced by the example plans |
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Consumer group for non-critical DSS queries. Referenced by the example plans |
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Consumer group for ETL jobs. Referenced by the example plans |
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Consumer group for interactive, OLTP operations. Referenced by the example plan |
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Consumer group for low-priority sessions. |
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Consumer group for maintenance tasks. |
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Default consumer group for all sessions that do not have an explicit initial consumer group, are not mapped to a consumer group with session-to-consumer group mapping rules, or are mapped to a consumer group that is not in the currently active resource plan.
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Consumer group for system administrators. It is the initial consumer group for all sessions created by user accounts |
Parent topic: Oracle Database Resource Manager Reference
27.13.2 Predefined Consumer Group Mapping Rules
Oracle Database includes predefined consumer group mapping rules.
Table 27-7 summarizes the consumer group mapping rules that are predefined in Oracle Database. You can verify these rules by querying the view DBA_RSRC_GROUP_MAPPINGS
. You can use the DBMS_RESOURCE_MANAGER
.SET_CONSUMER_GROUP_MAPPING
procedure to modify or delete any of these mapping rules.
Table 27-7 Predefined Consumer Group Mapping Rules
Attribute | Value | Mapped Consumer Group | Notes |
---|---|---|---|
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The session is running a backup operation with RMAN. The session is automatically switched to |
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The session is running a copy operation with RMAN. The session is automatically switched to |
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The session is performing a data load operation with Data Pump. The session is automatically switched to |
Parent topic: Oracle Database Resource Manager Reference
27.13.3 Resource Manager Data Dictionary Views
You can query a set of data dictionary views for information relating to database resource management.
Table 27-8 lists views that are associated with the Resource Manager.
Table 27-8 Resource Manager Data Dictionary Views
View | Description |
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Lists all resource consumer groups that exist in the database. |
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Lists all resource plan directives that exist in the database. |
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Lists all resource plans that exist in the database. |
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Lists all of the various mapping pairs for all of the session attributes. |
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Lists the current mapping priority of each attribute. |
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Displays historical information about resource plan activation. This view contains AWR snapshots of |
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Displays historical statistical information about consumer groups. This view contains AWR snapshots of |
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For each entry in the view |
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Displays information about active resource consumer groups. This view can be used for tuning. |
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Displays a history of resources consumed and cumulative CPU wait time (due to resource management) per consumer group for the past minute. |
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Displays a history of resources consumed and cumulative CPU wait time (due to resource management) per consumer group for the past hour on a minute-by-minute basis. If a new resource plan is enabled, the history is cleared. |
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Displays the names of all currently active resource plans. |
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Shows when Resource Manager plans were enabled or disabled on the instance. It helps you understand how resources were shared among the consumer groups over time. |
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Displays Resource Manager statistics for each session. Shows how the session has been affected by the Resource Manager. Can be used for tuning. |
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Lists session information for each current session. Specifically, lists the name of the resource consumer group of each current session. |
Parent topic: Oracle Database Resource Manager Reference