If your DB instance is a Multi-AZ deployment, you can force a failover from one availability zone toanother when you select the Reboot option. When you force a failover of your DB instance, AmazonRDS automatically switches to a standby replica in another Availability Zone and updates the DNSrecord for the DB instance to point to the standby DB instance. As a result, you will need to clean upand re-establish any existing connections to your DB instance. Reboot with failover is beneficial whenyou want to simulate a failure of a DB instance for testing, or restore operations to the original AZafter a failover occurs. Source: http://docs.aws.amazon.com/AmazonRDS/latest/UserGuide/USER_RebootInstance.html