Subject: Benefits and Usage of RMAN with Standby Databases
Doc ID: 602299.1
Applies to:
Oracle Server – Enterprise Edition – Version: 9.0.1.4 to 11.1.0.6
Information in this document applies to any platform.
Goal
Benefits and Usage of RMAN with Standby Databases
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Solution
RMAN can back up the standby database and its associated archived redo logs. Standby backups of datafiles and archived redo logs are fully interchangeable with primary database backups. In other words, you can run the RESTORE command to restore a backup of a standby datafile to the primary database, and you can restore a backup of a primary datafile to the standby database. The standby control file and primary control file, however, are not interchangeable. Although some files such as the control file and SPFILE must be backed up on the primary database.
Benefits of backing up database at standby site :
+ Because the standby database is not the production database, a standby backup does not interfere with transactions or batch jobs in the production database. Hence, you can use the standby database as a backup host without interfering with the production system.
+ If the standby and primary databases are on separate hosts, then standby backup operations do not consume CPU cycles, allocate memory, or consume other resources on the production host.
Note : Both the primary database and standby database should use the same recovery catalog. Even though these databases share the same DBID, RMAN is able to differentiate the standby database from the primary. Note that you do not need to register the standby database in the catalog if the primary is already registered: simply connect to the standby database and run the BACKUP command.
Backing Up a Standby Database with RMAN :
Use the RMAN BACKUP command to back up the standby database. A backup of the standby database is exactly the same as a backup of the primary database, except that the backup takes place on the standby site. The primary database has no influence on the backup of the standby database. Note that when you connect to the standby database to perform the backup, you connect using the TARGET keyword and not the AUXILIARY keyword.
As the following table shows, whether the standby database backup is consistent or inconsistent depends on the state of the standby database when the backup is made. Only a consistent backup can be restored without performing media recovery.
Standby Database Status Backup Status
Shutdown cleanly and then mounted (but not placed in recovery mode) Consistent
Mounted after instance failure or SHUTDOWN ABORT Inconsistent
Manual recovery mode Inconsistent
Managed recovery mode Inconsistent
Read-only mode Inconsistent
Example 1 : Performing a consistent/cold backup on the standby database :
sql> connect SYS/oracle@sbdb1
sql> SHUTDOWN IMMEDIATE
sql> STARTUP NOMMOUNT PFILE=initSTANDBY.ora
sql> ALTER DATABASE MOUNT STANDBY DATABASE;
$ rman target sys/oracle@sbdb1 catalog rmanUser/passwd@conn_catalog
RMAN> backup database;
RMAN> backup archivelog all;
Example 2 : Performing a inconsistent/hot backup on the standby database :
$ rman target sys/oracle@sbdb1 catalog rmanUser/passwd@conn_catalog
RMAN> backup database;
RMAN> backup archivelog all;
In Example 2 we are assuming that the database is in Managed recovery mode.
Note : The control file and SPFILE must be backed up on the primary database.