Beginners Guide to Flash Recovery Area in Oracle Database

This post discusses the below topics:

Benefits of using Flash Recovery Area.
Explains how to Create FRA using DB_RECOVERY_FILE_DEST_SIZE and DB_RECOVERY_FILE_DEST
Database Files that can reside in Flash Recovery Area.
How to Disable FRA

What is a Flash Recovery Area?

The flash recovery area can be defined as a single, unified storage area that keeps all the database recovery related files and performs recovery activities in an Oracle database. The flash recovery area is the most powerful tool available in Oracle 10g that plays a vital role in performing database recovery operations. The flash recovery area serves as the default storage area for all files related to backup and restore operations.

The flash recovery area provides the following benefits:

Single storage location for all recovery-related files.
Automatic management of recovery-related disk space.
Faster backup and restore operations, since you don’t need to restore tape backups.
Increased reliability of backups, since disks are generally safer storage devices than tapes.
Flash database is only possible when the Flash Recovery Area is configured.

Following are the various entities that can be considered as the flash recovery area:

A single directory
An entire file system
Automatic storage management (ASM)

Note: The flash recovery area is shared among databases in order to optimize the usage of disk space for database recovery operations. In case of a media failure or a logical error, the flash recovery area is referred to retrieve all the files needed to recover a database.

What’s in the Flash Recovery Area?

The flash recovery area may contain the following files:

Datafile copies

The new RMAN command BACKUP AS COPY can be used to create image copies of all datafiles and automatically store in the flash recovery area.

Control file autobackups

The database places any control file backups it generates in the flash recovery area.

Archived redo log files

If you store Archived redo log files in the flash recovery area, Oracle will automatically delete the files.

Online redo log files

Oracle recommends that you save a multiplexed copy of your online redo log files in the flash recovery area. The following statements can create online redo logs in the flash recovery area: CREATE DATABASE, ALTER DATABASE ADD LOGFILE, ALTER DATABASE ADD STANDBY LOGFILE, and ALTER DATABASE OPEN RESETLOGS.

Current control files

Oracle also recommends that you store a multiplexed current control file in the flash recovery area.

RMAN files

All the RMAN backups can be stored in Flash Recovery Area.

Flashback logs

If you enable the flashback database feature, Oracle copies images of each altered block in every datafile into flashback logs stored in the flash recovery area.

Note: Oracle calls the multiplexed redo log files and control files in the flash recovery area permanent files, since they should never be deleted and are part of the live database. Oracle terms all the other files in the flash recovery area (recovery related files) transient files, since Oracle will delete them eventually after they have become obsolete or have already been copied to tape.

Creating a Flash Recovery Area

You use the DB_RECOVERY_FILE_DEST and DB_RECOVERY_FILE_DEST_SIZE initialization parameters to configure a flash recovery area in your database. When you use the DB_RECOVERY_FILE_DEST parameter to specify the destination of your flash recovery area, you can use a directory, file system, or ASM disk group as your destination.

Dynamically Defining the Flash Recovery Area :

ALTER SYSTEM SET DB_RECOVERY_FILE_DEST_SIZE = 2G SCOPE=BOTH;
ALTER SYSTEM SET DB_RECOVERY_FILE_DEST = 'E:\RECOVERY_AREA' SCOPE=BOTH;

You must always specify the size parameter before specifying the location parameter.

Disabling the Current Flash Recovery Area

To disable the current flash recover area, use the below command:

SQL> ALTER SYSTEM SET DB_RECOVERY_FILE_DEST = '';

Note: even after you disable the flash recovery area, the RMAN will continue to access the files located in the flash recovery area for backup and recovery purposes.