Exchange 2013 circular logging question

vmdude used Ask the Experts™

We need to do a number of large mailbox moves and we are cautious of our log file location filling up between backup/truncation.

Can we enable circular logging on our databases (all of which are DAG protected) If so is there anything we need to be aware of before we do this?
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One thing to take into account. To enable circular logging you will need to dismount and then re mount each database
Top Expert 2015
Yes you can enable Circular logging on DB in a DAG and there is no need to dismount or mount subjected DB. just apply Circular logging settings and then wait for 5-10 mins logs will be truncated.

Now thing is about backup, when CL is enabled then you won't be able to incremental backup you will have to take full backup only. Circular logging has draw back that last full backup is the only source which can be restored in case of Disaster Recovery. So be aware about this.

Yes if you have large mailboxes and you have less space on drive so enable CL for once and move them then disable circular logging and start full back immediately.


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There is no need worrying about taking a full backup immediately after disabling circular logging if you have 4 database copies. There are enough copies for activation in case of failure. Exchange 2010 and 2013 uses CRCS or continuous replication circular logging in a DAG which runs of the replication service instead of traditional circular logging which worked off the JET database engine. If you have no database copies, it would default to tradition JET logging, requiring a db dismount remount. You do not need to worry about incremental backup, one full backup a week is fine. Microsoft fully supports a 4 db copy DAG with CL enabled. We have it set in production in a Exchange 2010 organization. Most admins do not know the difference between traditional vs CRCL as pretty evident in this post. Just use it and there is no need to worry about anything if you have enough db copies. Disable it when the mailboxes have moved.

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