Improving Incremental RMAN Backup
RMAN’s change tracking feature for incremental backups improves incremental backup performance by recording changed blocks in each datafile in a change-tracking file. If change tracking is enabled, RMAN uses the change-tracking file to identify changed blocks for incremental backup, thus avoiding the need to scan every block in the datafile. There is a new background process responsible for writing data to the block change- tracking file, which is called Block Change Writer CTWR.
Enabling and Disabling Change Tracking
You can enable or disable change tracing when the database is open. To alter the change tracking setting, you must use SQL* Plus to connect to the target database with administrator privileges.
- You can enable this tracking mechanism by issuing the following command:
SQL> ALTER DATABASE ENABLE BLOCK CHANGE TRACKING USING FILE ‘/w001/backup/ORCL/rman/change.log’;
This command creates a binary file called change.log for tracking purposes.
- To disable change tracking, use this SQL statement:
SQL>ALTER DATABASE DISABLE BLCOK CHANGE TRACKING;
- To see whether change tracking is currently enabled, you can query from SQL*Plus, you can query V$BLOCK_CHAGNE_TRACKING.
SQL> SELECT filename,status FROM V$ BLOCK_CHAGNE_TRACKING;