Database Reference
In-Depth Information
What happens if the Control File has lost the Backup Records
Most RMAN restores are easy and require only the use of the RMAN client. However,
we've seen cases where the RMAN client was not enough. In one case, the database site
had lost its recovery catalog, and the
CONTROL_FILE_RECORD_KEEP_TIME
parameter was
set to 7 days. Guess what happened to all the RMAN metadata after 7 days when the
recovery catalog was lost.
At the same time, we had a need to restore a database to a point in time of perhaps 30
days before to check on the state of some data. Of course, the metadata for the restore
was not available. This was clearly a bad day.
There are several ways to address this problem. The Oracle Database 12
c
RMAN
CATALOG
command provides the ability to catalog backup set pieces in the database (this was not
available prior to Oracle Database 10
g
). In the case of the loss listed earlier, we opted to
write some PL/SQL and use the PL/SQL packages that RMAN uses itself to restore the
backups from tape. RMAN uses a PL/SQL package called dbms_backup_restore to per-
form most backup and restore operations. Using this package (documented pretty well
on Oracle's support site at
metalink.oracle.com
), we were able to restore a database
from an older backup.
The bottom line is that as long as you have the backup set pieces, any RMAN backup
can be restored. It just might take some time and effort and perhaps a bit of help from
Oracle support.
When using a
RUN
block, you will use the
SET
command to set the recovery window for
RMAN, as shown in this example:
Run {
Set until time until time '09/30/2013:18:00:00';
Restore database;
Recover database;
}
You can do point-in-time recovery using the following:
Time
The
time-based point-in-time recovery
method is based on the timestamps in the
online redo logs. RMAN will restore the database to the closest possible timestamp listed
in the command. You can find the timestamp ranges contained in specific online redo logs
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