"Translated from MoS article" Flashback area and Flashback database

Flashback Zone and Flashback database

Reference from:
FLASH RECOVERY area and FLASHBACK database (document ID 369759.1)

Suitable for:
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 Zone

The Flashback zone (FRA) is a directory that provides a centralized disk location for backup and recovery files
Oracle creates archive logs in the FRA region. Rman can store backup in the Fra area, and by default, the FRA zone is where Rman backup is stored.

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

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

In addition, it is recommended to periodically backup the FRA area to tape, then you will have a closer backups on disk, older backups on tape

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

This differs from the traditional point-in-time recovery. To flashback a database,oracle use older block image to discard (back out) modifications to the database
This means that Oracle block is overwrite with its previous image to back up the database to a point in time past.

If flashback database is enabled, Oracle establishes a before image of flashback Log,databae Block before the block is stored to the Flashback log

Oracle Auto Create, delete, and flashback log in the Resize Fra area. You just need to care about Flashback log: Monitor performance and allocate how much disk space is allocated for the flashback log in the Fra area.

Flashback database is not a real media recovery because it does not involve the restore physical datafile. However, under some cases, Flashback is better than using 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 require a restore of the entire database.

You can limit the number of flashback logs by using the following parameters:
Db_flashback_retention_target (can be dynamically modified)--can put the database FLASHBACK how much minutes before. But you can't delete flashback logs manually, you need to turn flashback database off to delete flashback logs

For flashback log space management, see the MOS article:
Note 369755.1 Flashback logs-space Management

"Translated from MoS article" Flashback area and Flashback database