If I were a CQ systems administrator....
Write a script to monitor the repository folder. How big is it? How many tar files are in today? What is the difference between yesterday's tar files total & todays? The motivation for this is that sometimes you get a server increasing in disk space and its because the TAR optimser isn't running for long enough.
grep the logs for the "last stage" of the online backup.
similarly for the TAR optimiser completion step.