Local Oracle ASM clients with direct access to Oracle ASM disks (Standard Oracle ASM cluster)

With this mode, illustrated as Hub Node A in Figure 20-1, Oracle ASM continues to support existing standard architecture in which database clients are running with an Oracle ASM instance on the same host computer. The local client architecture is only supported on a Hub node.

Figure 20-1 Oracle Flex ASM Client Configurations

Description of "Figure 20-1 Oracle Flex ASM Client Configurations"

In this configuration, the database instances are on the same Hub node as the Oracle ASM instance and are referred to as local Oracle ASM client instances. Oracle ASM metadata moves between Oracle ASM and the database instances. This client has direct I/O access to Oracle ASM disks.

Local mode does not use Oracle Flex ASM, so clusters configured with local Oracle ASM do not require an Oracle ASM network, nor do they contain other Oracle Flex ASM services.

Oracle Flex ASM clients with direct access to Oracle ASM disks

With this mode, illustrated as Hub Node B in Figure 20-1, database clients that are running on Hub nodes of the Oracle ASM cluster access Oracle ASM remotely for metadata, but perform block I/O operations directly to Oracle ASM disks. The hosts running the Oracle ASM server and the remote database client must both be Hub nodes. A Hub node is a node in an Oracle ASM cluster that is tightly connected with other servers and has direct access to a shared disk.

In this configuration, the database instances are on different host computers than the nearby Oracle ASM instance, as shown on Hub Node C in Figure 20-1, and are referred to as Oracle ASM client instances.

The databases are in the same Oracle ASM cluster as the Oracle ASM instance and the database instances are located on a Hub node. Oracle ASM metadata moves between Oracle ASM and the database instance. This client has direct I/O access to Oracle ASM disks.

Depending on the distribution of database instances and Oracle ASM instances, a database client may access Oracle ASM locally on the same node or remotely over the Oracle ASM network. This mode of operation is used by database clients on Hub nodes in the Oracle ASM cluster. Direct access mode is also the only Oracle Flex ASM configuration supported by Oracle ASM cluster file system.

Oracle ACFS access through the Oracle ASM proxy instance

An Oracle ASM proxy instance is an Oracle instance running on a Hub node with a direct Oracle ASM client. An Oracle ASM proxy instance provides support for Oracle Automatic Storage Management Cluster File System (Oracle ACFS) and Oracle ASM Dynamic Volume Manager (Oracle ADVM).

Figure 20-2 shows the configuration of Oracle ACFS and Oracle ADVM with an Oracle ASM Proxy server in Oracle Flex ASM.

Figure 20-2 Oracle ACFS and Oracle ADVM in Oracle Flex ASM Configuration

Description of "Figure 20-2 Oracle ACFS and Oracle ADVM in Oracle Flex ASM Configuration"

The INSTANCE_TYPE initialization parameter is set to ASMPROXY for Oracle ASM proxy instances.

Oracle ACFS can also be used as a method of storage access for InDirect Storage Member Clusters. For information, refer to About Oracle ACFS in the Cluster Domain.

Network-based connectivity to Oracle ASM disk groups with Oracle IOServer (IOS)

An Oracle IOServer (IOS) instance provides Oracle ASM file access for Oracle Database instances on nodes of Oracle member clusters that do not have connectivity to Oracle ASM managed disks. For member clusters that do have connectivity to Oracle ASM managed disks, IOServer could be configured as a backup in the event of failure. An Oracle IOServer instance is used only with Oracle member clusters.

Figure 20-3 shows the relationship of Oracle IOServer and an Oracle Database in a member cluster.

Figure 20-3 Oracle IOServer Configuration

Description of "Figure 20-3 Oracle IOServer Configuration"

In addition, IOS enables you to configure client clusters on such nodes. On the storage cluster, an IOServer instance opens up network ports to which clients send their IO. The IOServer instance receives data packets from the client and performs the appropriate IO to Oracle ASM disks similar to any other database client. On the client side, databases can use dNFS to communicate with an IOServer instance. However, there is no client side configuration so you are not required to provide a server IP address or any additional configuration information. On nodes and clusters that are configured to access Oracle ASM files through IOServer, the discovery of the Oracle IOS instance occurs automatically.

The IOS instance contains the following processes:

• Network processes: These processes open up network ports and receive dNFS requests from the client side. These requests are then placed in a queue for IO and Identifier processes to pick up and process. Network processes also pick up responses from those other types of processes and send the response back to the client.

• Identifier processes: These processes pick up dNFS requests to create, delete, identify, unidentify, and resize Oracle ASM files.

• IO processes: These processes perform the actual IO on files that are identified by the local IOS instance.

The ASM_IO_PROCESSES initialization parameter specifies the number of IO worker processes to be started in an Oracle IO server instance. For information about the ASM_IO_PROCESSES initialization parameter, refer to ASM_IO_PROCESSES.

Displaying Information About Oracle Flex ASM

You can use the ASMCMD showclustermode command to determine whether Oracle Flex ASM is enabled. For example:

$ asmcmd showclustermode
ASM cluster : Flex mode enabled 

You can view Oracle Flex ASM connections with SQL*Plus and ASMCMD commands. Fore example:

SQL> SELECT instance_name, db_name, status FROM V$ASM_CLIENT;
INSTANCE_NAME   DB_NAME  STATUS
--------------- -------- ------------
+ASM1           +ASM     CONNECTED
orcl1           orcl     CONNECTED
orcl2           orcl     CONNECTED

$ asmcmd lsct data
DB_Name  Status    Software_Version  Compatible_version  Instance_Name  Disk_Group
+ASM     CONNECTED       19.0.0.0.0          19.0.0.0.0  +ASM           DATA
orcl     CONNECTED       19.0.0.0.0          19.0.0.0.0  orcl1          DATA
orcl     CONNECTED       19.0.0.0.0          19.0.0.0.0  orcl2          DATA

SRVCTL and CRSCTL Commands to Administer Oracle Flex ASM

SRVCTL is extended to enable an administrator to create or change attributes of Oracle Clusterware resources. You can use SRVCTL to determine the status of the instances in an Oracle Flex ASM configuration. For example:

$ srvctl status asm -detail
ASM is running on mynoden02,mynoden01
ASM is enabled.

You can also use SRVCTL to determine whether Oracle Flex ASM is enabled. If enabled, then srvctl config asm displays the number of Oracle ASM instances that has been specified for use with the Oracle Flex ASM configuration. For example:

$ srvctl config asm
ASM instance count: 3

You can modify the Oracle ASM instance count, or cardinality, with the SRVCTL modify asm command. For example:

$ srvctl modify asm -count 4

$ srvctl modify asm -count ALL

Clients are automatically relocated to another instance if an Oracle ASM instance fails. If necessary, clients can be manually relocated.

The SRVCTL UPDATE INSTANCE and SRVCTL UPDATE IOSERVER commands can change the Oracle ASM instance for a database, or the Oracle IOServer instance for a database, or the Oracle ASM instance for an Oracle IOServer. For example:

$ srvctl update instance -db my_orcl_db -instance my_instance_1 -targetinstance my_asm_instance_1

$ srvctl update ioserver -instance my_instance_2 -targetinstance my_asm_instance_2

You can run the SRVCTL STATUS commands with the -detail option to display which Oracle ASM instance or Oracle IOserver instance each client is connected to.

Every database user must have a wallet with credentials to connect to Oracle ASM. CRSCTL commands can be used by the database user to manage this wallet. All Oracle ASM user names and passwords are system generated.

You can run SRVCTL commands to manage Oracle ASM networks and listeners. For example, as the root user you can add an Oracle ASM network using srvctl add asmnetwork, with or without the optional network mask.

# srvctl add asmnetwork -netnum 1 -subnet nnn.nn.nn.n/255.255.255.0

# srvctl add asmnetwork -netnum 2 -subnet nnn.nn.nn.n

As the root or as CRS user, you can check the status or configure the Oracle ASM network with srvctl config asmnetwork.

$ srvctl config asmnetwork
ASM network 1 exists
Subnet IPv4: nnn.nn.nn.n/255.255.255.0/
Subnet IPv6:
Network is enabled
Network is individually enabled on nodes:
Network is individually disabled on nodes:
ASM network 2 exists
Subnet IPv4: nnn.nn.nn.n//
Subnet IPv6:
Network is enabled
Network is individually enabled on nodes:
Network is individually disabled on nodes:

As the CRS user, you can add an Oracle ASM listener with srvctl add listener You can use the default listener name (LISTENER_ASM) or specify a name for the listener.

$ srvctl add listener -asmlistener -netnum 1

$ srvctl add listener -asmlistener -netnum 2 -listener listener2

You can check the status of the Oracle ASM listener with srvctl config listener.

$ srvctl config listener -asmlistener
Name: LISTENER2_ASM
Type: ASM Listener
Owner: msmith
Subnet: nnn.nn.nn.n
Home: <CRS home>
End points: TCP:1526
Listener is enabled.
Listener is individually enabled on nodes:
Listener is individually disabled on nodes:
Name: LISTENER_ASM
Type: ASM Listener
Owner: msmith
Subnet: nnn.nn.nn.n
Home: CRS_hOME
End points: TCP:1525
Listener is enabled.
Listener is individually enabled on nodes:
Listener is individually disabled on nodes:

As the root user, you can run the srvctl modify asmnetwork command with the -deptype option to specify the dependency type (mandatory or optional) for Oracle ASM networks. The -deptype setting enables you to determine whether or not you want to tolerate the unavailability of any network.

• The -deptype mandatory option specifies a mandatory dependency on a Oracle ASM network. This means that the system does not tolerate the loss of that network. If only one of the Oracle ASM networks connects both the cluster nodes and Oracle ASM client clusters, then that network should be specified as mandatory because the Oracle ASM client clusters cannot run when that network is not available. For example:

  # srvctl modify asmnetwork -netnum 2 -deptype mandatory

• The -deptype optional option specifies an optional dependency on a Oracle ASM network. This means that the system can tolerate the loss of that network. If there are multiple Oracle ASM networks that only connect the cluster nodes, then you can specify them as optional to tolerate the failure of one of the networks. The optional value is the default setting for -deptype in Oracle ASM 19c. For example:

  # srvctl modify asmnetwork -netnum 2 -deptype optional

Relocating a Client With ALTER SYSTEM

You can use the ALTER SYSTEM RELOCATE CLIENT command to relocate a client. For example:

SQL> ALTER SYSTEM RELOCATE CLIENT 'client-id';

In the previous SQL statement, client-id is of the form instance_name:db_name. The INSTANCE_NAME and DB_NAME columns are contained in the V$ASM_CLIENT view. You must connect as SYSASM to the Oracle ASM instance to run the SQL statement. When you issue this statement, the connection to the client is terminated and the client fails over to the least loaded instance. If the client is currently connected to the least loaded instance, then the connection to the client is terminated and the client fails over to that same instance.

ASMCMD Commands to Manage Member Clusters

You can use ASMCMD commands to administer the configuration of member clusters.

You can list member clusters with the lscc command and remove member clusters with the rmcc command.

You create a member cluster with the mkcc command or change a member cluster with the chcc command. For example, you can change the storage method from direct Oracle ASM to indirect Oracle ASM, or change from indirect Oracle ASM to direct Oracle ASM using the ASMCMD chcc and mkcc commands.

Initialization Parameters for Oracle Flex ASM

There are no new initialization parameters specifically for instances in an Oracle Flex ASM configuration; however, the settings of existing parameters should be reviewed and possibly adjusted for the Oracle Flex ASM environment.

The value of the INSTANCE_TYPE initialization parameter specifies the type of instance, including Oracle ASM proxy instances. In addition to ASM and RDBMS values, the ASMPROXY value identifies Oracle ASM proxy instances.