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Using RMAN Incremental Backups to Roll Forward a Physical Standby Database (Oracle 10g) (03-March-2011)
There are several scenarios that can occur in an Oracle Data Guard configuration which renders a physical standby database as either unusable or invalid. For example, an extended network failure can occur between the primary and standby machines which cause the standby database to fall significantly far behind the primary database. If the necessary archived redo log files needed to synchronize the physical standby database with the primary database are no longer available, log gap resolution will be unable to resolve the gap in the redo stream to catch up the standby. Another popular scenario exists when a DML or DDL operation is performed on the primary database using the NOLOGGING or UNRECOVERABLE clause and the FORCE LOGGING database option is not enabled on the primary. If the FORCE LOGGING database option is not enabled, then Oracle will not log the entire operation in the redo log and thus, never send the modified data to the standby database for recovery. While this doesn't necessarily render the entire standby database as unusable, it does invalidate the standby for those tables affected and may require substantial DBA administrative activities to repair. Although you can specify the ALTER DATABASE FORCE LOGGING statement on the primary database to override the NOLOGGING clause and prevent this type of damage to occur in the future, this statement will not repair a standby database that has already been invalidated. In each of the scenarios listed above, one solution would be to simply delete and formally re-create the physical standby database to enter it back into the Data Guard configuration. Depending on the size of the database, rebuilding the standby database could be an expensive operation as it would potentially involve a lot of time and resources making this a nonviable option. The following guide presents a quick and efficient alternative to rebuilding a physical standby database in Oracle Database 10g Release 2 by using RMAN incremental backups to roll forward and resynchronize a physical standby database with the primary database. Using the RMAN BACKUP INCREMENTAL FROM SCN command, you can create an incremental backup on the primary database that starts at the standby database's current SCN, which can then be used to roll the standby database forward in time. Using RMAN Incremental Backups to Roll Forward a Physical Standby Database (Oracle 10g) This guide will provide step-by-step recovery procedures which cover the following three scenarios: o Physical Standby Database Lags Far Behind the Primary Database o Physical Standby Database Has Nologging Changes On a Subset of Datafiles o Physical Standby Database Has Widespread Nologging Changes ---------------------------- Jeffrey M. Hunter, OCP Sr. Database Administrator email@example.com http://www.idevelopment.info ----------------------------