After you upgrade Availability replicas in an Always On Availability Group to Cumulative Update 1 for SQL Server 2016, you may experience low transactional throughput on the primary replica. Additionally, an error that resembles the following is logged in the error log of the Sync secondary replica:
Error: 19432, Severity: 16, State: 0.
Always On Availability Groups transport has detected a missing log block for availability database "database_name". LSN of last applied log block is (xxxx:xxxxxxx:x). Log scan will be restarted to fix the issue. This is an informational message only. No user action is required.
The fix for this issue is included in the following 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:
Microsoft has confirmed that this is a problem in the Microsoft products that are listed in the "Applies to" section.
Learn about the terminology that Microsoft uses to describe software updates.