Symptoms
Assume that you set up a database mirroring session in SQL Server 2012,2014 or 2016. You add a witness to support automatic failover. In a rare situation, the mirroring session may stop, and then the data is no longer synchronized. Additionally, an automatic failover doesn’t occur as expected.
Resolution
Update information
This issue is fixed in the following cumulative updates for SQL Server:
Cumulative Update 2 for SQL Server 2016 SP1
Cumulative Update 4 for SQL Server 2016
Cumulative Update 3 for SQL Server 2014 SP2
Cumulative Update 10 for SQL Server 2014 SP1
Cumulative Update 6 for SQL Server 2012 Service Pack 3
Recommendation: Install the latest cumulative update for SQL Server
Each new cumulative update for SQL Server contains all the hotfixes and all the security fixes that were included with the previous cumulative update. Check out the latest cumulative updates for SQL Server:
Latest cumulative update for SQL Server 2016
Latest cumulative update for SQL Server 2014 SP1/SP2
Latest cumulative update for SQL Server 2012 SP3
Workaround
To work around this issue, resume the mirroring session. To do this, type each of the following Transact-SQL statements, and then press Enter after each statement:
ALTER DATABASE database_name SET PARTNER SUSPEND
GO
ALTER DATABASE database_name SET PARTNER RESUME
GO
Status
Microsoft has confirmed that this is a problem in the Microsoft products that are listed in the "Applies to" section.
References
Learn about the terminology that Microsoft uses to describe software updates.