Configuring RMAN - Oracle RMAN for Absolute Beginners - page 112

■ Note See Chapter 5 for details on how to back up a database using incremental backups.

18. Using Incrementally Updated Backups
Incrementally updated backups are an efficient way to implement an image copy backup strategy. This technique
instructs RMAN to first create image copies of data files; then, the next time the backup runs, instead of creating a
fresh set of image copies, RMAN makes an incremental backup (changes to blocks since the image copy was created)
and applies that incremental backup to the image copies.
If you have the disk space available for full image copies of your database and you want the flexibility to use the
image copies directly, in the event of a media failure, consider this backup strategy.
One potential disadvantage of this approach is that if you're required to restore and recover to some point in
the past, you can only restore and recover to the point at which the image copies were last updated with the
incremental backup.

■ Note See Chapter 5 for details on how to back up a database using incrementally updated backups.

19. Using Block Change Tracking
This feature keeps track of when a database block changes. The idea is that if you're using an incremental backup
strategy, you can enhance performance, because by implementing this feature, RMAN doesn't have to scan each
block (under the high-water mark) in the data files to determine whether it needs to be backed up. Rather, RMAN
only has to access the block change tracking file to find which blocks have changed since the last backup and directly
access those blocks. If you work in a large, data warehouse environment and are using an incremental backup
strategy, consider enabling block change tracking to enhance performance.

■ Note See Chapter 5 for details on how to implement block change tracking.

20. Configuring Binary Compression
You can configure RMAN to use true binary compression when generating backup sets. You can enable compression
in one of two ways:

AS COMPRESSED BACKUPSET with the BACKUP command. • Specify

CONFIGURE command.
Here is an example of backing up with compression when issuing the BACKUP command:

• Use a one-time

RMAN> backup as compressed backupset database;

In this example, compression is configured for the disk device:

RMAN> configure device type disk backup type to compressed backupset;