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10. Restoring and Recovering with Recovery Manager
Performing Recovery with a Backup Control File and No Recovery Catalog
This section assumes that you have RMAN backups of the control file, but do not use a recovery catalog. Assuming that you enabled the control file autobackup feature for the target database, you can restore an autobackup of the control file. Because the autobackup uses a default format, RMAN can restore it even though it does not have a repository available that lists the available backups. You can restore the autobackup to the default or a new location. RMAN replicates the control file to all CONTROL_FILES locations automatically.
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Note:
If you know the backup piece name (for example, from the media manager or because the piece is on disk), then you can specify the piece name using the RESTORE CONTROLFILE FROM 'filename' command. The server records the location of every autobackup in the alert log.
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Because you are not connected to a recovery catalog, the control file must have a record of all needed backups. If any backups are not listed in the control file, then RMAN cannot restore them. If datafile copies are located on disk but are not in the control file, however, then you can add them to the control file repository with the CATALOG command. This cataloging procedure is described in "Cataloging Archived Logs and User-Managed Copies".
Because the repository is not available when you restore the control file, run the SET DBID command to identify the target database. You should only run the SET DBID command in the following specialized circumstances:
You are not connected to a recovery catalog and want to restore the control file or server parameter file.
You are connected to a recovery catalog want to restore the control file, but the database name is not unique in the recovery catalog.
The server parameter file is lost and you want to restore it.
To recover the database with an autobackup of the control file without a recovery catalog:
Start RMAN and connect to the target database. For example, run:
CONNECT TARGET /
Start the target instance without mounting the database. For example:
STARTUP NOMOUNT;
Set the database identifier for the target database with SET DBID. RMAN displays the DBID whenever you connect to the target. You can also obtain it by running LIST, querying the catalog, or looking at the filenames of control file autobackup. (refer to "Restoring When Multiple Databases in the Catalog Share the Same Name: Example"
. For example, run:
SET DBID 676549873;
Restore the autobackup control file, then perform recovery. Do the following:
Optionally, specify the most recent backup time stamp that RMAN can use when searching for a control file autobackup to restore.
[B]If a nondefault format was used to create the control file, then specify a nondefault format for the restore of the control file. [/B]
If the channel that created the control file autobackup was device type sbt, then you must allocate one or more sbt channels. Because no repository is available, you cannot use automatic channels. If the autobackup was created on a disk channel, however, then you do not need to manually allocate a channel.
Restore the autobackup of the control file, optionally setting the maximum number of days backward that RMAN can search (up to 366) and the initial sequence number that it should use in its search for the first day.
Mount the database. Note that because the repository is now available, any automatic channels that you configured are also available.
If the online logs are inaccessible, then restore and recover the database as described in "Performing Incomplete Restore and Recovery". You must terminate recovery by setting the UNTIL clause to a time, log sequence, or SCN before the online redo logs. If the online logs are usable, then restore and recover the database as described in "Performing Complete Restore and Recovery".
In this example, the online redo logs have been lost. This example limits the restore of the control file autobackup, then performs recovery of the database to log sequence 13243, which is the most recent archived log:
RUN
{
# Optionally, set upper limit for eligible time stamps of control file backups
# SET UNTIL TIME '09/10/2000 13:45:00';
# Specify a nondefault autobackup format only if required
# SET CONTROLFILE AUTOBACKUP FORMAT FOR DEVICE TYPE DISK TO '?/oradata/%F.bck';
ALLOCATE CHANNEL c1 DEVICE TYPE sbt; # manually allocate one or more channels
RESTORE CONTROLFILE FROM AUTOBACKUP
MAXSEQ 100 # start at sequence 100 and count down
MAXDAYS 180; # start at UNTIL TIME and search back 6 months
ALTER DATABASE MOUNT DATABASE;
}
# uses automatic channels configured in restored control file
RESTORE DATABASE UNTIL SEQUENCE 13243;
RECOVER DATABASE UNTIL SEQUENCE 13243; # recovers to most recent archived log
If recovery was successful, then open the database and reset the online logs:
ALTER DATABASE OPEN RESETLOGS;
It is recommended that you immediately back up the database, preferably with the database mounted (to avoid possible data loss in an open database). Because the database is a new incarnation, the backups made before the RESETLOGS are not easily usable. For example, enter:
SHUTDOWN IMMEDIATE
STARTUP MOUNT
BACKUP DATABASE;
ALTER DATABASE OPEN;
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