Oracle: block change trackingΒΆ

Title:Oracle: block change tracking
Author:Douglas O’Leary <dkoleary@olearycomputers.com>
Description:Oracle: block change tracking
Date created:07/27/2010
Date updated:07/27/2010
Disclaimer:Standard: Use the information that follows at your own risk. If you screw up a system, don’t blame it on me...

Block change tracking is used in conjunction with incremental backups. The block change tracking file, as you might imagine, is used to track the changes at the block level to each of the datafiles.

The block change tracking file size is automatically determined. It should be roughly 1/30,000 of the database size. The absolute minimum size is 320k per datafile so the file for my little database will be 5*320/1024 = 1.56 megs. The file will hold enough data to support 8 days of incremental backups. Your base backup, then, has to be done minimally, once a week.

  1. To enable block change tracking:

    alter database enable block change tracking
    using file '${absolute_path}' [ reuse ]
    
  2. To disable block change tracking:

    alter database disable block change tracking
    
  3. To identify status of block change tracking:

    SQL> select * from v$block_change_tracking;
    
    STATUS     FILENAME                                           BYTES
    ---------- --------------------------------------------- ----------
    DISABLED
    or
    SQL> select * from v$block_change_tracking;
    
    STATUS     FILENAME                                           BYTES
    ---------- --------------------------------------------- ----------
    ENABLED    /oracle/block_change/oci1_bc.fil                11599872