Truncate them yourself if space is an issue before the proper backup strategy is in place. There are few ways to do this. Check out the eseutil docs.
From: NP Sent: Thursday, July 27, 8:50 AM Subject: [Exchange] Changing logging to Circular and back? To: exchange@lists.myitforum.com Apparently we had a miscommunication between departments and our backup guys were only doing a DB copy when backing up our 2013 DB’s so logs haven’t been getting trunked for months. That equals about 2TB’s of log files. I’m not sure how to dig myself out of this (if we can’t get a full backup with logs so they are deleted) other than maybe turning circular logging on for a short time and letting Exchange clean them up. Will Exchange even clean them up or will we still need to manually delete? Thanks Niles