Databases Reference
In-Depth Information
Chapter 22
RMAN in an Oracle Data Guard
Environment
You can use RMAN to simplify the administration of your Oracle Data Guard setup. You can employ all the standard
RMAN backup and recovery strategies in a Data Guard environment. RMAN lets you perform backups on the primary
database and enables quick recovery from the loss of data files, control files, or even the entire database.
It's important to understand that RMAN commands work similarly across both the primary and the standby
database. You can back up a tablespace, for example, on a primary database and restore and recover that tablespace
in a standby database and vice versa. The recovery catalog keeps track of which database files and which backup files
belong to which database, by associating all database and backup files with a
db_unique_name
.
RMAN treats disk backups and tape backups differently when it comes to accessibility. It considers disk backups
accessible only to the database with which the backup is associated. The recovery catalog considers tape backups
created on one database as accessible to all databases. You can copy a backup from a standby server to a primary server
and vice versa and catalog the backup in the server where you moved the backup. Once you connect as target to the
database on the destination server and catalog the backup, that backup file will be associated with the target database.
Since only a physical standby is a block-by-block copy of the primary database, you can't use a logical database to
back up your primary database.
Synchronizing a Physical Standby Database
Problem
You want to synchronize a physical standby database with the primary database.
Solution
You can use RMAN incremental backups to synchronize a physical standby database with its primary database. Here
are the steps to follow:
1.
Stop the application of redo on the standby database:
SQL> alter database recover managed standby database cancel;
2.
If the standby database has lagged far behind the primary database, find the current SCN
of the standby database by executing the following query (on the standby database):
SQL> select current_scn from v$database;
