Overview of the Backup and Redo Failover Feature
In an environment where Backup and Redo Failover is configured, a protected database sends backups and redo to a primary Recovery Appliance under normal circumstances. When that appliance is unavailable, the protected database sends backups and redo to an alternate Recovery Appliance until service on the primary is restored.
The alternate appliance does not create virtual full backups from the temporary backups it receives; it only stores the backup pieces (incremental and archived log backups). When the primary appliance is back online and operational, the alternate appliance forwards all temporary backups to the primary appliance, which uses them to create the corresponding virtual full backups. After all virtual full backups are created, the protected database resumes sending backups and redo to the primary appliance. The alternate appliance deletes the temporary backup pieces from local storage only after they are successfully forwarded to the primary appliance.