ALTER DATABASE ERROR IN MIRRORING.
We got the below error in Mirroring when we are trying to add WITNESS server to the existing asynchronous operating mode. 1) In my environment PRINCIPAL and MIRROR servers are SQL Server 2014 Enterprise edition, but WITNESS server was SQL Server 2014 Express edition . 2) SQL Service accounts are running with NT Service\MSSQLSERVER account where as WITNESS server is running with another account( NT Service\MSSQL$VM ) . --> 3) But all these accounts are communicating with one another successfully. But if we are using the same DOMAIN account for all the instances(PRINCIPAL,MIRROR and WITNESS) there would be very less chance that we are going to get error. Work Around: The issue resolved when we STOP and RESTART the endpoint of WITNESS server . Though it is a express edition this works fine for us. No need to hesitate even though you dont find end point in server objects of express edition. SELECT * FROM sys.database_mirroring_endpoints GO ALT