Content remains in the IDOL content database until you purge it (that is, delete it). This is done using the IDOL database management command line utility, IdolMgr, to purge content databases based on their age.
For example, you can schedule regular IdolMgr jobs to purge databases that are more than six months old. This allows you to maintain a rolling six-month history of indexed documents.
It has been noticed that when executing a purge of the IDOL CI system the purge succeeds but the Database space is not reclaimed.