Enabling Block Change Tracking

Block changing tracking improves the performance of incremental backups by recording changed blocks in the block change tracking file. During an incremental backup, instead of scanning all data blocks to identify which blocks have changed, RMAN uses this file to identify the changed blocks that need to be backed up.

You can enable block change tracking when the database is either open or mounted. This section assumes that you intend to create the block change tracking file as an Oracle Managed File in the database area, which is where the database maintains active database files such as data files, control files, and online redo log files.

To determine if block change tracking is enabled, check the STATUS and FILENAME columns in the V$BLOCK_CHANGE_TRACKING view, using the following statement from the SQL or RMAN prompt:

SELECT status, filename FROM V$BLOCK_CHANGE_TRACKING;

To enable block change tracking:

  1. Connect RMAN to the target database as described in "Connecting to the Target Database Using RMAN."
  2. Determine the current location of the database data files by submitting the following query: 
    RMAN> SELECT NAME FROM V$DATAFILE;
 
NAME
-----------------------------------------------
/u01/app/oracle/oradata/orcl/system01.dbf
/u01/app/oracle/oradata/orcl/example01.dbf
/u01/app/oracle/oradata/orcl/sysaux01.dbf
/u01/app/oracle/oradata/orcl/undotbs01.dbf
/u01/app/oracle/oradata/orcl/users01.dbf

    In this example, the query results show that data files are stored in the file system in the directory /u01/app/oracle/oradata/orcl. Data files might also be stored in an Oracle Automatic Storage Management disk group.

  3. Set the DB_CREATE_FILE_DEST initialization parameter to specify the location where new database files, including the block change tracking file, must be stored. You can specify the same directory shown in query results from the previous step, with the final portion of the path—the database SID—stripped, as shown in the following example, or designate a new directory. Any directory that you specify must have the write permission for the Oracle software owner.

    The following command specifies that new database files must be stored in the directory /u01/app/oracle/oradata/:

    ALTER SYSTEM SET DB_CREATE_FILE_DEST = '/u01/app/oracle/oradata';
  4. Enable block change tracking for the database using the following command: 
    ALTER DATABASE ENABLE BLOCK CHANGE TRACKING;

See Also: