The file names of Oracle Managed Files comply with the Optimal Flexible Architecture (OFA) standard for file naming.

The assigned names are intended to meet the following requirements:

• Database files are easily distinguishable from all other files.

• Files of one database type are easily distinguishable from other database types.

• Files are clearly associated with important attributes specific to the file type. For example, a data file name may include the tablespace name to allow for easy association of data file to tablespace, or an archived log name may include the thread, sequence, and creation date.

No two Oracle Managed Files are given the same name. The name that is used for creation of an Oracle managed file is constructed from three sources:

• The default creation location

• A file name template that is chosen based on the type of the file. The template also depends on the operating system platform and whether or not Oracle Automatic Storage Management is used.

• A unique string created by Oracle Database or the operating system. This ensures that file creation does not damage an existing file and that the file cannot be mistaken for some other file.

As a specific example, file names for Oracle Managed Files have the following format on a Solaris file system:

destination_prefix/o1_mf_%t_%u_.dbf

where:

• destination_prefix is destination_location/db_unique_name/datafile

  where:

  • destination_location is the location specified in DB_CREATE_FILE_DEST

  • db_unique_name is the globally unique name (DB_UNIQUE_NAME initialization parameter) of the target database. If there is no DB_UNIQUE_NAME parameter, then the DB_NAME initialization parameter value is used.

• %t is the tablespace name.

• %u is an eight-character string that guarantees uniqueness

For example, assume the following parameter settings:

DB_CREATE_FILE_DEST   = /u01/app/oracle/oradata
DB_UNIQUE_NAME = PAYROLL

Then an example data file name would be:

/u01/app/oracle/oradata/PAYROLL/datafile/o1_mf_tbs1_2ixh90q_.dbf

Names for other file types are similar. Names on other platforms are also similar, subject to the constraints of the naming rules of the platform.

The examples on the following pages use Oracle managed file names as they might appear with a Solaris file system as an OMF destination.

The CREATE DATABASE statement can perform actions related to Oracle Managed Files.

• Specifying Control Files at Database Creation
  At database creation, the control file is created in the files specified by the CONTROL_FILES initialization parameter.
• Specifying Redo Log Files at Database Creation
  The LOGFILE clause is not required in the CREATE DATABASE statement, and omitting it provides a simple means of creating Oracle managed redo log files.
• Specifying the SYSTEM and SYSAUX Tablespace Data Files at Database Creation
  The DATAFILE or SYSAUX DATAFILE clause is not required in the CREATE DATABASE statement, and omitting it provides a simple means of creating Oracle managed data files for the SYSTEM and SYSAUX tablespaces.
• Specifying the Undo Tablespace Data File at Database Creation
  The DATAFILE subclause of the UNDO TABLESPACE clause is optional and a file name is not required in the file specification.
• Specifying the Default Temporary Tablespace Temp File at Database Creation
  The TEMPFILE subclause is optional for the DEFAULT TEMPORARY TABLESPACE clause and a file name is not required in the file specification.
• CREATE DATABASE Statement Using Oracle Managed Files: Examples
  Examples illustrate creating a database with the CREATE DATABASE statement when using the Oracle Managed Files feature.

Redo log files are created at database creation time. They can also be created when you issue either of the following statements: ALTER DATABASE ADD LOGFILE and ALTER DATABASE OPEN RESETLOGS.

• Using the ALTER DATABASE ADD LOGFILE Statement
  The ALTER DATABASE ADD LOGFILE statement lets you later add a new group to your current redo log.
• Using the ALTER DATABASE OPEN RESETLOGS Statement
  If you previously created a control file specifying RESETLOGS and either did not specify file names or specified nonexistent file names, then the database creates redo log files for you when you issue the ALTER DATABASE OPEN RESETLOGS statement.

Archived logs are created by a background process or by a SQL statement.

DB_RECOVERY_FILE_DEST_SIZE = 20G
DB_RECOVERY_FILE_DEST      = '/u01/oradata'
LOG_ARCHIVE_DEST_1         = 'LOCATION=USE_DB_RECOVERY_FILE_DEST'

Unlike files that are not managed by the database, when an Oracle managed data file or temp file is dropped, the file name is removed from the control file and the file is automatically deleted from the file system.

When an Oracle managed redo log file is dropped, its Oracle Managed Files are deleted. You specify the group or members to be dropped.

With Oracle Managed Files, SQL statements that rename files do not actually rename the files on the operating system, but rather, the names in the control file are changed.

The data files, control files, and redo log files in a standby database can be managed by the database. This is independent of whether Oracle Managed Files are used on the primary database.

When recovery of a standby database encounters redo for the creation of a data file, if the data file is an Oracle managed file, then the recovery process creates an empty file in the local default file system location. This allows the redo for the new file to be applied immediately without any human intervention.

When recovery of a standby database encounters redo for the deletion of a tablespace, it deletes any Oracle managed data files in the local file system. Note that this is independent of the INCLUDING DATAFILES option issued at the primary database.

An example illustrates creating and managing a database with multiplexed redo logs.

1. Setting the initialization parameters

   The DBA includes three generic file creation defaults in the initialization parameter file before creating the database. Automatic undo management mode (the default) is also specified.

   DB_CREATE_FILE_DEST = '/u01/oradata'
   DB_CREATE_ONLINE_LOG_DEST_1 = '/u02/oradata'
   DB_CREATE_ONLINE_LOG_DEST_2 = '/u03/oradata'
   UNDO_MANAGEMENT = AUTO
   

   The DB_CREATE_FILE_DEST parameter sets the default file system directory for the data files and temp files.

   The DB_CREATE_ONLINE_LOG_DEST_1 and DB_CREATE_ONLINE_LOG_DEST_2 parameters set the default file system directories for redo log file and control file creation. Each redo log file and control file is multiplexed across the two directories.

2. Creating a database

   Once the initialization parameters are set, the database can be created by using this statement:

   SQL> CREATE DATABASE sample
   2>   DEFAULT TEMPORARY TABLESPACE dflttmp;
   

   Because a DATAFILE clause is not present and the DB_CREATE_FILE_DEST initialization parameter is set, the SYSTEM tablespace data file is created in the default file system (/u01/oradata in this scenario). The file name is uniquely generated by the database. The file is autoextensible with an initial size of 100 MB and an unlimited maximum size. The file is an Oracle managed file. A similar data file is created for the SYSAUX tablespace.

   Because a LOGFILE clause is not present, two redo log groups are created. Each log group has two members, with one member in the DB_CREATE_ONLINE_LOG_DEST_1 location and the other member in the DB_CREATE_ONLINE_LOG_DEST_2 location. The file names are uniquely generated by the database. The log files are created with a size of 100 MB. The log file members are Oracle Managed Files.

   Similarly, because the CONTROL_FILES initialization parameter is not present, and two DB_CREATE_ONLINE_LOG_DEST_n initialization parameters are specified, two control files are created. The control file located in the DB_CREATE_ONLINE_LOG_DEST_1 location is the primary control file; the control file located in the DB_CREATE_ONLINE_LOG_DEST_2 location is a multiplexed copy. The file names are uniquely generated by the database. They are Oracle Managed Files. Assuming there is a server parameter file, a CONTROL_FILES initialization parameter is generated.

   Automatic undo management mode is specified, but because an undo tablespace is not specified and the DB_CREATE_FILE_DEST initialization parameter is set, a default undo tablespace named UNDOTBS is created in the directory specified by DB_CREATE_FILE_DEST. The data file is a 20 MB data file that is autoextensible. It is an Oracle managed file.

   Lastly, a default temporary tablespace named dflttmp is specified. Because DB_CREATE_FILE_DEST is included in the parameter file, the temp file for dflttmp is created in the directory specified by that parameter. The temp file is 100 MB and is autoextensible with an unlimited maximum size. It is an Oracle managed file.

   The resultant file tree, with generated file names, is as follows:

   /u01
        /oradata
             /SAMPLE
                  /datafile
                       /o1_mf_system_cmr7t30p_.dbf
                       /o1_mf_sysaux_cmr7t88p_.dbf
                       /o1_mf_sys_undo_2ixfh90q_.dbf
                       /o1_mf_dflttmp_157se6ff_.tmp
   /u02
        /oradata
             /SAMPLE
                  /onlinelog
                       /o1_mf_1_0orrm31z_.log
                       /o1_mf_2_2xyz16am_.log
                  /controlfile
                       /o1_mf_cmr7t30p_.ctl
   /u03
        /oradata
             /SAMPLE
                  /onlinelog
                       /o1_mf_1_ixfvm8w9_.log
                       /o1_mf_2_q89tmp28_.log
                  /controlfile
                       /o1_mf_x1sr8t36_.ctl
   

   The internally generated file names can be seen when selecting from the usual views. For example:

   SQL> SELECT NAME FROM V$DATAFILE;
   
   NAME
   ----------------------------------------------------
   /u01/oradata/SAMPLE/datafile/o1_mf_system_cmr7t30p_.dbf
   /u01/oradata/SAMPLE/datafile/o1_mf_sysaux_cmr7t88p_.dbf
   /u01/oradata/SAMPLE/datafile/o1_mf_sys_undo_2ixfh90q_.dbf
   
   3 rows selected
   

3. Managing control files

   The control file was created when generating the database, and a CONTROL_FILES initialization parameter was added to the parameter file. If needed, then the DBA can re-create the control file or build a new one for the database using the CREATE CONTROLFILE statement.

   The correct Oracle managed file names must be used in the DATAFILE and LOGFILE clauses. The ALTER DATABASE BACKUP CONTROLFILE TO TRACE statement generates a script with the correct file names. Alternatively, the file names can be found by selecting from the V$DATAFILE, V$TEMPFILE, and V$LOGFILE views. The following example re-creates the control file for the sample database:

   CREATE CONTROLFILE REUSE
     DATABASE sample
     LOGFILE 
       GROUP 1('/u02/oradata/SAMPLE/onlinelog/o1_mf_1_0orrm31z_.log', 
               '/u03/oradata/SAMPLE/onlinelog/o1_mf_1_ixfvm8w9_.log'), 
       GROUP 2('/u02/oradata/SAMPLE/onlinelog/o1_mf_2_2xyz16am_.log',
               '/u03/oradata/SAMPLE/onlinelog/o1_mf_2_q89tmp28_.log')
     NORESETLOGS
     DATAFILE '/u01/oradata/SAMPLE/datafile/o1_mf_system_cmr7t30p_.dbf',
              '/u01/oradata/SAMPLE/datafile/o1_mf_sysaux_cmr7t88p_.dbf',
              '/u01/oradata/SAMPLE/datafile/o1_mf_sys_undo_2ixfh90q_.dbf',
              '/u01/oradata/SAMPLE/datafile/o1_mf_dflttmp_157se6ff_.tmp'
     MAXLOGFILES 5
     MAXLOGHISTORY 100
     MAXDATAFILES 10
     MAXINSTANCES 2
     ARCHIVELOG;
   

   The control file created by this statement is located as specified by the CONTROL_FILES initialization parameter that was generated when the database was created. The REUSE clause causes any existing files to be overwritten.

4. Managing the redo log

   To create a new group of redo log files, the DBA can use the ALTER DATABASE ADD LOGFILE statement. The following statement adds a log file with a member in the DB_CREATE_ONLINE_LOG_DEST_1 location and a member in the DB_CREATE_ONLINE_LOG_DEST_2 location. These files are Oracle Managed Files.

   SQL> ALTER DATABASE ADD LOGFILE;
   

   Log file members continue to be added and dropped by specifying complete file names.

   The GROUP clause can be used to drop a log group. In the following example the operating system file associated with each Oracle managed log file member is automatically deleted.

   SQL> ALTER DATABASE DROP LOGFILE GROUP 3;
   

5. Managing tablespaces

   The default storage for all data files for future tablespace creations in the sample database is the location specified by the DB_CREATE_FILE_DEST initialization parameter (/u01/oradata in this scenario). Any data files for which no file name is specified, are created in the file system specified by the initialization parameter DB_CREATE_FILE_DEST. For example:

   SQL> CREATE TABLESPACE tbs_1;
   

   The preceding statement creates a tablespace whose storage is in /u01/oradata. A data file is created with an initial of 100 MB and it is autoextensible with an unlimited maximum size. The data file is an Oracle managed file.

   When the tablespace is dropped, the Oracle Managed Files for the tablespace are automatically removed. The following statement drops the tablespace and all the Oracle Managed Files used for its storage:

   SQL> DROP TABLESPACE tbs_1;
   

   Once the first data file is full, the database does not automatically create a new data file. More space can be added to the tablespace by adding another Oracle managed data file. The following statement adds another data file in the location specified by DB_CREATE_FILE_DEST:

   SQL> ALTER TABLESPACE tbs_1 ADD DATAFILE;
   

   The default file system can be changed by changing the initialization parameter. This does not change any existing data files. It only affects future creations. This can be done dynamically using the following statement:

   SQL> ALTER SYSTEM SET DB_CREATE_FILE_DEST='/u04/oradata';
   

6. Archiving redo information

   Archiving of redo log files is no different for Oracle Managed Files, than it is for unmanaged files. A file system location for the archived redo log files can be specified using the LOG_ARCHIVE_DEST_n initialization parameters. The file names are formed based on the LOG_ARCHIVE_FORMAT parameter or its default. The archived logs are not Oracle Managed Files.

7. Backup, restore, and recover

   Since an Oracle managed file is compatible with standard operating system files, you can use operating system utilities to backup or restore Oracle Managed Files. All existing methods for backing up, restoring, and recovering the database work for Oracle Managed Files.

An example illustrates creating and managing a database with both database and fast recovery areas.

1. Setting the initialization parameters

   The DBA includes the following generic file creation defaults:

   DB_CREATE_FILE_DEST = '/u01/oradata'
   DB_RECOVERY_FILE_DEST_SIZE = 10G
   DB_RECOVERY_FILE_DEST = '/u02/oradata'
   LOG_ARCHIVE_DEST_1 = 'LOCATION = USE_DB_RECOVERY_FILE_DEST'
   

   The DB_CREATE_FILE_DEST parameter sets the default file system directory for data files, temp files, control files, and redo logs.

   The DB_RECOVERY_FILE_DEST parameter sets the default file system directory for control files, redo logs, and RMAN backups.

   The LOG_ARCHIVE_DEST_1 configuration 'LOCATION=USE_DB_RECOVERY_FILE_DEST' redirects archived logs to the DB_RECOVERY_FILE_DEST location.

   The DB_CREATE_FILE_DEST and DB_RECOVERY_FILE_DEST parameters set the default directory for log file and control file creation. Each redo log and control file is multiplexed across the two directories.

2. Creating a database
3. Managing control files
4. Managing the redo log
5. Managing tablespaces

   Tasks 2, 3, 4, and 5 are the same as in Scenario 1, except that the control files and redo logs are multiplexed across the DB_CREATE_FILE_DEST and DB_RECOVERY_FILE_DEST locations.

6. Archiving redo log information

   Archiving online logs is no different for Oracle Managed Files than it is for unmanaged files. The archived logs are created in DB_RECOVERY_FILE_DEST and are Oracle Managed Files.

7. Backup, restore, and recover

   An Oracle managed file is compatible with standard operating system files, so you can use operating system utilities to backup or restore Oracle Managed Files. All existing methods for backing up, restoring, and recovering the database work for Oracle Managed Files. When no format option is specified, all disk backups by RMAN are created in the DB_RECOVERY_FILE_DEST location. The backups are Oracle Managed Files.

An example illustrates adding Oracle Managed Files to an existing database.

1. Setting the initialization parameters

   To allow automatic data file creation, set the DB_CREATE_FILE_DEST initialization parameter to the file system directory in which to create the data files. This can be done dynamically as follows:

   SQL> ALTER SYSTEM SET DB_CREATE_FILE_DEST = '/u03/oradata';
   

2. Creating tablespaces

   Once DB_CREATE_FILE_DEST is set, the DATAFILE clause can be omitted from a CREATE TABLESPACE statement. The data file is created in the location specified by DB_CREATE_FILE_DEST by default. For example:

   SQL> CREATE TABLESPACE tbs_2;
   

   When the tbs_2 tablespace is dropped, its data files are automatically deleted.