If you manage a Lync 2013 server, you probably have looked through event viewer to find this little bugger; Event 21054.
You’ll notice this event is generated whenever the address book is updated with Update-CsAddressBook cmdlet or after the maintenacne that is run every day.
The following is a sample of the event log information details:
Users are not indexed in the database that should be.
Expected indexed user count: 0
Actual indexed user count: 136
Cause: User replication issue.
Resolution:
Run Update-CsAddressBook to synchronize all accounts.
How lovely, it didn’t resolve the issue. All googling will state run “debug-csaddressbookreplication” and if not indexed objects and Abandonded objects are 0 then…..
You guessed it! MS favorite quote “You can safely ignore it.”
Better yet MS fix this already!
Jan 2018 Update
I have no clue if this is still a problem, I generally don’t look in event viewer unless somethings broken. However if you are running Zenos, PRTG or some other monitoring software that ties into some windows servers event viewer, you’d have to filter it there.