To easily
recover from the loss of all control file copies, you should configure RMAN to
take automatic backups of the control file. The automatic backup of the control
file occurs independently of any backup of the current control file explicitly
requested as part of your backup command. If you are running RMAN in NOCATALOG
mode, it is highly recommended that you activate control file autobackup.
Otherwise, if you lose your control file, your database may be unrecoverable.
To
configure control file autobackup, modify the backup policy for your database
by using Enterprise Manager or use the following RMAN command:
CONFIGURE CONTROLFILE
AUTOBACKUP ON;
By default,
control file autobackups are disabled. If you enable control file autobackups,
then RMAN automatically backs up the control file and the current server
parameter file (if used to start up the database) in one of two circumstances:
•
A
successful backup is recorded in the RMAN repository.
•
A
structural change to the database affects the contents of the control file,
which, therefore, must be backed up.
The control
file autobackup file name has a default format of %F for all device types, so
that RMAN can infer the file location and restore it without a repository. This
variable format translates into c-IIIIIIIIII-YYYYMMDD-QQ, where:
•
IIIIIIIIII
stands for the DBID
•
YYYYMMDD
is a time stamp of the day the backup is generated
•
QQ
is the hex sequence that starts with 00 and has a maximum of FF
You can
change the default format by using the CONFIGURE CONTROLFILE AUTOBACKUP FORMAT
FOR DEVICE TYPE type TO 'string' command. The value of string
must contain the substitution variable %F and cannot contain other substitution
variables. For example:
CONFIGURE CONTROLFILE
AUTOBACKUP FORMAT
FOR DEVICE TYPE DISK TO
'/u01/oradata/cf_ORCL_auto_%F';
Control
file autobackups are stored in the Flash Recovery Area, unless otherwise
specified.
With a
control file autobackup, RMAN can recover the database even if the current
control file, recovery catalog, and server parameter file are inaccessible.
Because the path used to store the autobackup follows a well-known format, RMAN
can search for and restore the server parameter file or control file from that
autobackup.
