In the event of a planned or unplanned outage of your DB instance, Amazon RDS    automatically switches to a standby replica in another Availability Zone if you have enabled Multi-AZ. The automatic    failover mechanism simply changes the DNS record of the DB    instance to point to the standby DB instance. As a result, you will need to re-establish any     existing connections to your DB instance.  High availability does not mean    that Amazon keeps, for example, two databases running in parallel; it is the data on    disk that is replicated. If the primary DB instance becomes unavailable, a failover    begins and the database software is started on the standby replica. The time it takes    for the failover to complete depends on the database activity and other conditions at    the time the primary DB instance became unavailable. When the failover is complete, it    can take additional time for the RDS console UI to reflect the new Availability    Zone.  Amazon RDS handles ...