[Translated from mos] flashback and flashback database,

[Translated from mos] flashback and flashback database,

Flashback zone and flashback database

Reference:
Flash recovery area and FLASHBACK database (Document ID 369759.1)

Applicable:
Oracle Database-Enterprise Edition-Version 10.1.0.2 and later
Information in this document applies to any platform.
* ** Checked for relevance on 16-Apr-2014 ***

Solution:

Flash back area

The flash back area (FRA) is a directory that provides a centralized disk location for backup and recovery files
Oracle creates an archive log in FRA. Rman stores backups in FRA. By default, FRA stores rman backups.

All files necessary to recover the database following a media failure are located in the flash recovery area (if defined ).

FRA also acts as the disk cache for tape. The recommended policy is to store backups in FRA so that more recent backups are available on disk, so that the backup and restore processes will be faster.

In addition, we recommend that you periodically back up FRA to tape, so you will have closer backups on disk and older backups on tape.

Flash back database
This is a new feature introduced from 10 Gb. This feature provides a way to revert the database to a previous time point. You can forward a single table revert to the past.

This is different from the traditional point-in-time recovery ). To flashback a database, oracle uses the older block image to discard (back out) changes to the database.
This means that the Oracle block is overwritten with its previous image to back the database to a previous time point.

If the flashback database is enabled, the flashback log is created in Oracle during normal database operations. The before image of the databae block will be stored in the flashback log before the block applies any change.

The flashback log in auto create, delete, and resize FRA of Oracle. You only need to pay attention to the following: monitoring performance and how much disk space is allocated to the flashback log in FRA.

Flashback database is not a true media recovery, because it does not involve restore physical datafile. However, in some cases, Flashback is better than restore and recover.
(Flashback is preferable to using the RESTORE and RECOVER commands in some cases ). Because Flashback is faster and easier, and does not need to restore the entire database.

You can use the following parameters to limit the number of flashback logs:
DB_FLASHBACK_RETENTION_TARGET (which can be dynamically modified) --> before how many minutes can be stored in database flashback. However, you cannot manually delete the flashback logs. You must disable the flashback database before deleting the flashback logs.

For more information about flashback log space management, see the mos article:
Note 369755.1 Flashback Logs-Space management