As part of a troubleshooting process, I had to disable circular logging on a Microsoft Exchange 2013 mailbox database, that was part of a Database Availability Group (DAG). What is circular logging? Microsoft Exchange uses log files that record all transactions and modifications to a mailbox database. In this case, Exchange works like MS SQL or Oracle. These log files are used, to bring the database back to a consistent state after a crash, or to recover a database to a specific point-in-time.