Data Guard 11G

posted Feb 24, 2011, 6:08 AM by Sachchida Ojha   [ updated Feb 24, 2011, 6:10 AM ]
Data Guard standby databases provide high return on investment by also supporting ad-hoc queries, reporting, backups, or test activity, while providing disaster protection. Specifically:

• The Active Data Guard option, first available with Oracle Database 11g, enables a physical standby database to be used for read-only applications while simultaneously receiving updates from the primary database. Queries executed on an active standby database receive up-to-date results.

• Snapshot Standby enables a physical standby database to be open read-write for testing or any activity that requires a read-write replica of production data. A Snapshot Standby continues to receive, but not apply, updates generated by the primary. These updates are applied to the standby database automatically when the Snapshot Standby is converted back to a physical standby database. Primary data is protected at all times.

• A logical standby database has the additional flexibility of being open read-write. While data that is being maintained by SQL Apply cannot be modified, additional local tables can be added to the database, and local index structures can be created to optimize reporting, or to utilize the standby database as a data warehouse, or to transform information used to load data marts.

• Standby databases can be used to perform planned maintenance in a rolling fashion. Maintenance is first performed on a standby database. Production is switched over to the standby database when the maintenance tasks are completed. The only downtime is the time needed to effect a switchover operation. This increases availability and reduces risk when performing hardware or O.S. maintenance, site maintenance, or when upgrading to new database patchsets, full database releases, or implementing other significant database changes.

• A physical standby database, because it is an exact replica of the primary database, can also be used to offload the primary database of the overhead of performing backups.
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