Flash recovery area management

11.1 view fra location

SQL> show parameters db_recovery_file_dest

NAME TYPE VALUE

-----------------------------------------------------------------------------

Db_recovery_file_dest string

Db_recovery_file_dest_size big integer 0

Select * from v $ recovery_file_dest

NAME

--------------------------------------------------------------------------------

SPACE_LIMIT SPACE_USED SPACE_RECLAIMABLENUMBER_OF_FILES

-----------------------------------------------------

+ DGFRA

471859200 0 0 0

11.2 modify the fra position and size

SQL> alter system setdb_recovery_file_dest_size = 450 m scope = both;

System altered.

SQL> alter system setdb_recovery_file_dest = '+ dgfra' scope = both;

System altered.

If you want to modify the position first, an error is returned.

SQL> alter system setdb_recovery_file_dest = '+ dgfra ';

ERROR at line 1:

ORA-02097: parameter cannot be modifiedbecause specified the value is invalid

ORA-19802: cannot use DB_RECOVERY_FILE_DESTwithout DB_RECOVERY_FILE_DEST_SIZE

After viewing the changes:

SQL> show parameter db_recovery_file_dest;

NAME TYPE VALUE

-----------------------------------------------------------------------------

Db_recovery_file_dest string + DGFRA

Db_recovery_file_dest_size large integer 450 M

11.3 cancel the crash recovery zone of fra

SQL> alter database flashback off;

Database altered.

SQL> alter system setdb_recovery_file_dest = '';

System altered.

SQL> show parameter db_recovery

NAME TYPE VALUE

-----------------------------------------------------------------------------

Db_recovery_file_dest string

Db_recovery_file_dest_size large integer 450 M

B _RECOVERY_FILE_DEST_SIZE can be cleared only after DB_RECOVERY_FILE_DEST is cleared.

11.4 fra parameters:

Db_recovery_file_dest: Specifies the position of the flash recovery zone.

Db_recovery_file_dest_size: Specifies the available space size of the flash recovery zone.

Db_flashback_retention_target: specifies the time when the database can be rolled back. The unit is minute. The default value is 1440 minutes,

SQL> show parameter db_flashback

NAME TYPE VALUE

-----------------------------------------------------------------------------

Db_flashback_retention_target integer 1440

That is, one day. Of course, the rollback time is also determined by the size of the flash recovery zone, because the flash log required for rollback is saved.

11.5 flash recovery zone content

All recovery-related files can be stored in the Flash recovery zone.

SQL> select file_type fromv $ flash_recovery_area_usage;

All types of files listed in the query results in the preceding view can be stored and managed in the Flash recovery area.

In some 10 Gb dynamic views (V $ CONTROLFILE, V $ LOGFILE, V $ ARCHIVED_LOG, V $ DATAFILE_COPY, etc.), the new column IS_RECOVERY_DEST_FILE, specifies whether the relevant files are in the recovery area.

Automatic disk-based backup and recovery,

The following files can be stored in the Flash recovery area:

• Control Files

• Archived log files (Note: After the flashrecovery area is set in the Oracle manual, the value of LOG_ARCHIVE_DEST_10 is automatically set to the location of the flash recovery area, this change is not observed during the test)

• Flashback logs

• Automatic backup of control files and spfiles

• RMAN backup set

• Copy data files

As mentioned above, the flash recovery area provides a centralized storage area, which greatly reduces management overhead. This is the main advantage. It can be used with RMAN for quick recovery.

If the upper limit is set, you are not afraid to use up DGFRA.