BDA supports rolling updates for SQL Server Instances hosting SQL Server Availability Groups, which is the process of patching SQL Server instances in series and failing over the primary replica in the middle and at the end of the series. Selecting all instances hosting an Availability Group automatically triggers this function. If you select some, but not all, of the instances hosting an Availability Group, BDA will prompt you to remind you of this function. In BDA 8.9, this function is supported for instances hosting a single Availability Group only. For more information, see .

When patching SQL Server Instances which participate in a SQL Server Availability Group, if you do not select all the instances participating in the Availability Group, BDA will prompt you to indicate that there are more instances that should be patched. If you continue after receiving this prompt, BDA will patch the selected instances without performing any of the steps necessary to maintain high availability for the Availability Group.

When patching a set of SQL Server Instances that host replicas for an AlwaysOn Availability Group, BDA polls the Availability Group to see if all its databases are synchronized and, if not, continues to poll until 30 minutes has elapsed. If the databases are synchronized, it exits successfully. If the maximum time has elapsed and the databases are not synchronized, BDA displays a failure message, but the operation will still exit successfully.

The maximum polling time can be changed in the new GAC_Max_Wait_For_AvGrp_Synchronization custom variable using a time interval in seconds.