http://henrysluiman.blogspot.nl/2012/02/enable-circular-logging-in-exchange.html

Enable or Disable Circular Logging in Exchange 2010 By default circular logging is disabled but there are some cases where Circular logging can be helpful, for example when migrating a large amount of mailboxes from an older Exchange version to Exchange 2010. Through EMC

1. Under Organization Configuration click on Mailbox;
2. Click on Database Management where you find Databases;
3. Take properties by right click and under maintenance tab apply check of Enable circular logging.

Or Through PowerShell Set-MailboxDatabase -CircularloggingEnabled:$true However, remember to re-disable it when done. Set-MailboxDatabase -CircularloggingEnabled:$false The Information Store must be restarted for either of these changes to take place!