Thanks, that did the trick for me.  In our current set-up, this table is growing faster than the built-in clean-up process deletes from it.  As a result, syscommittab is slowly growing, and it's starting to impact CHANGETABLE query performance.  We're looking at the possibility of using the method described in this post to do an occasional clean-up of the table, until we upgrade to SQL Server 2017 (there were some improvements to the CT clean up process in SS2017, outlined here, that I think will solve our problems).  Outside of change tracking, are you aware of any gotchyas or concerns when manually deleting from sys.syscommittab in this way?  Online documentation indicates that the table is used for other purposes outside of change tracking.