FIGURE 12-3 RMAN persistent parameters in OEM
430 Oracle Database 11g DBA Handbook
Retention Policy
Backups can be automatically retained and managed using one of two methods: by a recovery
window or by redundancy. Using a recovery window, RMAN will retain as many backups as
necessary to bring the database to any point in time within the recovery window. For example,
with a Recovery Window of seven days, RMAN will maintain enough image copies, incremental
backups, and archived redo logs to ensure that the database can be restored and recovered to any
point in time within the last seven days. Any backups that are not needed to support this recovery
window are marked as OBSOLETE and are automatically removed by RMAN if a flash recovery
area is used and disk space is needed for new backups.
In contrast, a redundancy retention policy directs RMAN to retain the specified number of
backups or copies of each datafile and control file. Any extra copies or backups beyond the
number specified in the redundancy policy are marked as OBSOLETE. As with a recovery window,
obsolete backups are automatically removed if disk space is needed and a flash recovery area is
used. Otherwise, you can use the delete obsolete command to remove the backup files and update
the catalog.
If the retention policy is set to NONE, no backups or copies are ever considered obsolete, and
the DBA must manually remove unneeded backups from the catalog and from disk.
Pages:
645
646
647
648
649
650
651
652
653
654
655
656
657
658
659
660
661
662
663
664
665
666
667
668
669