DR Primary Sites Scenario 1 - Loss of a Database Server
For an environment using SQL Always On, a minimum of 2 synchronous-commit replicas is assumed. In the event that the replica holding the primary role fails, the secondary replica may be set to automatically (or manually) become the new primary. In general use, secondary replicas are used for redundancy only; all read/write database operations are handled by the primary replica. In the event that a local listener is unavailable, U-Series Appliances may be easily configured to point to an alternate database listener.
For a more comprehensive set of failover scenarios please see Always On availability groups: a high-availability and disaster-recovery solution.
For catastrophic failure of all database components it is necessary to restore from an offline backup of the database to a secondary or tertiary data center.