# Oracle Data Guard

An Oracle Data Guard configuration contains a production (primary) and standby database so that you have high availability in the case of a disaster. The standby database becomes the primary database when the primary database has a planned or unplanned outage.

In the Commvault environment, you can use Unified Data Guard for either a single-instance Oracle database or an Oracle RAC database. The Commvault support is considered "unified" because it intelligently supports Oracle Data Guard for both single-instance Oracle databases and Oracle RAC databases. Therefore, you can use the procedures in this section for both types of Oracle databases.

When you configure the Commvault software for Oracle Data Guard, the software discovers the database role (primary or standby) and then picks the appropriate client backup plan or the appropriate instance backup plan for the data and the log backups. You can configure the software to run the database and the log backups on different instances that also have different roles.

You configure an Oracle Data Guard pseudoclient that contains all the primary and standby nodes. The nodes can be on the same or different data centers. By default, the software uses the pseudoclient backup plan as the subclient backup plan.

You can configure backup plans for the physical clients that host the primary and standby servers. When the primary and standby servers are at different data centers and a failover occurs, the software cannot use the backup plans that you configured for the pseudoclient, because it needs access to a local MediaAgent. After a failover, the software uses the physical client backup plans and automatically reconfigures them to use the location aware MediaAgent.

You can make backups of the standby database even if the primary database has read-only tablespaces and you want to make backups of the standby database using the "Skip Read Only" option. RMAN does not natively support skipping read-only tablespaces when running backups on standby databases; if it is attempted the job fails and the following error is output:

    RMAN-06131: SKIP OFFLINE and SKIP READONLY are only allowed with current control file

Commvault software intelligently omits any read-only tablespaces when making the backup, which allows the backup to complete successfully.

Note

- You must use the RMAN recovery catalog so that the primary database knows about the backups that you performed on the standby databases.

- Disk caching of archive log backups is not supported with Unified Data Guard configurations.

- All the clients in the Data Guard environment should be at the same Commvault release level for the best operation of the Data Guard configuration.

- For a catalog-connected Oracle database, perform both data and log backups from a single client, preferably the first standby node.

- If a recovery catalog is not used, it is recommended to perform both data and log backups on the primary database.

- It is recommended to use consistent schemas across the primary and multiple standby databases. Cascaded standby databases aren't supported.

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