Persistent Severity 016 alerts: "Change Tracking autocleanup is blocked on side table" We had a large database running on a SQL Server 2014 Enterprise instance (evaluation license). Due to cost constraints, we had to move it to a new SQL Server 2017 Standard instance (per-core license; just updated to CU6). EDIT: The database is in SQL Server 2014 (120) compatibility, and was transferred by restoring full and log backups.

Everything is working fine except for change tracking. We use change tracking to locate recent changes and keep a denormalized table up to date; the denorm table is used for rapid filling of a grid for the web application.

Change tracking is working, but apparently autocleanup is not. We are getting Severity 016 alerts:


  Change Tracking autocleanup is blocked on side table of tablename. If the failure persists, check if the table tablename is blocked by any process.


These come about every half hour for each of the tables that is complaining (about 4 different tables).

We've tried the manual cleanup described here ... it too presents "side table is blocked" errors. 

So here are my choices:


Turn off this specific alert and hope nothing blows up.
Turn off autocleanup; schedule a manual cleanup during a daily maintenance window.
Not sure what else I can do.


Besides "what should I do to stop this?", my side question is "why is this happening with 2017 Std when it didn't happen with 2014 Enterprise?"
It seems to be a known issue and has already been recognized by Microsoft. You may read resolution as below:

Resolution 


  A fix for this issue is included in the following updates
  for SQL Server:
  
  Cumulative Update 10 for SQL Server 2017
  
  Cumulative Update 3 for SQL Server 2016 Service Pack 2
  
  Cumulative Update 1 for SQL Server 2014 Service Pack 3 
  
  With this fix, you will not see continuous messages any longer. The
  frequency of the error 22123 messages, if any, will not be more than
  once every 30 minutes. To completely eliminate these messages, enable
  trace flag 8293.


Listed are the version which has this issues: 


  
  SQL Server 2017 Developer
  SQL Server 2017 Enterprise
  SQL Server 2017 Enterprise Core
  SQL Server 2017 Standard Windows
  SQL Server 2016 Developer
  SQL Server 2016 Enterprise
  SQL Server 2016 Enterprise Core
  SQL Server 2016 Standard
  SQL Server 2014 Developer
  SQL Server 2014 Enterprise
  SQL Server 2014 Enterprise Core
  SQL Server 2014 Standard
  


Please read more from link.

Hope above helps.