Question: How much downtime can I expect during a maintenance window for my RDS for SQL Server Single-AZ or Multi-AZ instance?

I have an upcoming scheduled maintenance window for my Amazon Relational Database Service (Amazon RDS) for Microsoft SQL Server Single-AZ or Multi-AZ instance. What downtime should I expect during the maintenance window?Short descriptionAWS performs periodic maintenance to the physical host hardware, database version, or the operating system of your Amazon RDS for SQL Server instance. Before maintenance occurs, you receive an email notification. This email details the affected resources, and the scheduled timeframe of the maintenance.Estimated downtime differs for Single-AZ instances and Multi-AZ instances. Also, the downtime that you experience might change depending on the type of maintenance being performed.Note: You can review past scheduled maintenance for your RDS instances by viewing RDS events. Or, you can use the describe-pending-maintenance-actions AWS Command Line Interface (AWS CLI) command or the DescribeDBInstances for the RDS API.

ResolutionYou can verify if upcoming maintenance will incur downtime by checking your Personal Health Dashboard. The PHD will state if this maintenance involves downtime for the affected instances.You can check for pending or upcoming maintenance by checking the instance in the RDS console. For more information, see Viewing pending maintenance.You can adjust the time of your maintenance window. For more information, see Adjusting the preferred DB instance maintenance window.Hardware maintenance downtimeSingle-AZ instances: The instance is unavailable for several minutes while maintenance is performed. The exact time the maintenance takes varies depending on the instance class type and database size.Multi-AZ instances: Multi-AZ instances are unavailable for the time that it takes the primary instance to failover. This failover takes no more than 60 seconds. If only the secondary Availability Zone is affected by the maintenance, then there is no failover or downtime.Database engine upgrade downtimeSingle-AZ instances: The instance is unavailable for several minutes while maintenance is performed. The exact time the maintenance takes varies depending on the instance class type and database size.Multi-AZ instances: In Multi-AZ instances, both the primary and standby instances are upgraded. Amazon RDS performs rolling upgrades. So, you have an outage only for the duration of a failover after the secondary is upgraded and promoted to primary. The original primary (now the secondary) then has the upgrade applied to it.OS maintenance downtimeSingle-AZ instances: The instance is unavailable for several minutes while maintenance is performed. The exact time the maintenance takes varies depending on the instance class type and database size.Multi-AZ instances: In Multi-AZ RDS instances, both the primary and standby instances are upgraded. RDS performs rolling upgrades. So, you have an outage only for the duration of a failover after the secondary is upgraded and promoted to primary. The original primary (now the secondary) then has the upgrade applied to it.

Related informationWhat do I need to know about the Amazon RDS maintenance window?