An incremental backup backups up only those blocks that have changed since a previous backup.
Incremental backups have provided the following benefits:
1. Reduced disk space usage (smaller backup-pieces generated)
2. Somewhat faster backup completion times – Even though the number
of blocks eventually written to the backup-piece were less, Oracle
still had to read all the blocks to determine if they changed or not.
Oracle 10g offers a new feature, called block change tracking.
This feature allows for faster creation of incremental backups.
Changes to the database blocks are now tracked using a ‘tracking file’.
When the block change tracking is enabled, Oracle logs changes to the blocks
in this tracking file. During the incremental backup, RMAN reads the tracking
file to determine changed blocks. This obviates the need to read each and
every block in a datafile and thus results in faster incremental backups.