Oracle block-change tracking let's us do incremental backups for only the blocks that have been changed. To check the effectiveness, use the following query:
SELECT file#, avg(datafile_blocks), avg(blocks_read), avg(blocks_read/datafile_blocks)*100 AS PCT_READ_FOR_BACKUP, avg(blocks)
FROM V$BACKUP_DATAFILE
WHERE used_change_tracking='YES' and incremental_level>0
GROUP BY file#
Ideally we wanted to see the PCT_READ_FOR_BACKUP with a small value. If this value is very large, we can increase the frequency of incremental backups.
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