RMAN incremental backups : tracking changed blocks
Here's excerpt from 10g documentation :
"Change-Aware Incremental Backups
By using a new type of log file to track blocks that have changed in the database, Recovery Manager (RMAN) can avoid scanning the entire datafile during an incremental backup. Instead, the amount of data scanned is proportional to the amount of data changed."
Got a question though - What "log file" are they referring to? How do they keep track of changed blocks?
FYI - For the benefit of all. Something I recently read.
Obviously, I'm having an easy day with so many posts..
10g uses a file, analogous to journals in filesystems, to track the blocks that have changed since the last backup. RMAN reads this file to determine which blocks are to be backed up.
You can enable this tracking mechanism by issuing the following command:
SQL> alter database enable block change tracking using file '/rman_bkups/change.log';
This command creates a binary file called /rman_bkups/change.log for tracking purposes. Conversely, you can disable tracking with
SQL> alter database disable block change tracking;
To see whether change tracking is currently enabled, you can query:
SQL> select filename, status from v$block_change_tracking;
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