Symptoms
Assume that you have AlwaysOn Availability Groups configured in SQL Server 2014 or 2016. If an application uses the TABLOCK hint, the Service Broker Usage Control Service (UCS) task leaks memory. In this situation, you can see that the number of tasks in the sys.dm_os_tasks function continuously grows. This causes AlwaysOn synchronization to become slow.
Cause
This problem occurs because the UCS task leak may cause Lock Monitor to consume more CPU usage.
Resolution
This problem was first fixed in the following cumulative updates for SQL Server:
Cumulative Update 7 for SQL Server 2014 Service Pack 1
Cumulative Update 1 for SQL Server 2014 SP2
Cumulative Update 2 for SQL Server 2016
About cumulative updates 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 2014
Latest cumulative update for SQL Server 2016
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 Microsoft uses to describe software updates.