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RMAN Performance – Block Change Tracking

A new feature within Oracle 10g is the ability to improve the performance of your RMAN incremental backups by using BLOCK CHANGE  TRACKING.

The block change tracking feature uses a file stored on the file system to record which blocks have changed since the last backup. Then, when RMAN starts its backup, it can read the file to know which blocks to backup.

This file is to RMAN backups what an index is to a table. It helps identify specific blocks to backup, which reduces CPU and disk usage, thereby improving performance.

You can enable or disable change tracking when the database is either open or mounted. To store the change tracking file in the database area, set DB_CREATE_FILE_DEST in the target database. Then issue the following SQL statement to enable change tracking:

ALTER DATABASE ENABLE BLOCK CHANGE TRACKING;
ALTER DATABASE ENABLE BLOCK CHANGE TRACKING
    USING FILE ‘/mydir/rman_change_track.f’ REUSE;

If the change tracking file was stored in the database area, then it is deleted when you disable change tracking. You can use the following SQL to disable tracking:

ALTER DATABASE DISABLE BLOCK CHANGE TRACKING;

The V$BLOCK_CHANGE_TRACKING dynamic view shows information about this feature. Make sure that you are happy with how it works before enabling this in your production environment and test it out somewhere first.

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Category: RMAN


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