While its primary purpose is the limit the amount of disk space
used by the flash recovery area on the specified disk group or file system directory, it can be
temporarily increased once an alert is received to give the DBA additional time to allocate more
disk space to the disk group or relocate the flash recovery area.
Short of receiving a warning or critical alert, you can be a bit more proactive in monitoring
the size of the flash recovery area using the dynamic performance view V$RECOVERY_FILE_DEST
to see the total used and reclaimable space on the destination file system. In addition, you can use
the dynamic performance view V$FLASH_RECOVERY_AREA_USAGE to see a usage breakdown
by file type:
SQL> select * from v$recovery_file_dest;
NAME SPACE_LIMIT SPACE_USED SPACE_RECLAIMABLE NUMBER_OF_FILES
-------------------- ----------- ---------- ----------------- ---------------
+RECOV 8589934592 1595932672 71303168 13
SQL> select * from v$flash_recovery_area_usage;
FILE_TYPE PERCENT_SPACE_USED PERCENT_SPACE_RECLAIMABLE NUMBER_OF_FILES
--------------- ------------------ ------------------------- ---------------
CONTROL FILE .12 0 1
REDO LOG 1.87 0 3
ARCHIVED LOG .83 1 7
BACKUP PIECE 15.75 0 2
IMAGE COPY 0 0 0
FLASHBACK LOG 0 0 0
FOREIGN ARCHIVE 0 0 0
D LOG
7 rows selected.
SQL>
In this example, the flash recovery area is less than 20 percent used, with the largest
percentage due to RMAN backups.
414 Oracle Database 11g DBA Handbook
Performing Online Database Backups
Once a database is running in ARCHIVELOG mode, you can back it up while it is open and
available to users.
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