This topic explains how to use the Exchange Management Console or the Exchange Management Shell to enable or disable circular logging for a storage group. Circular logging is a method of conserving hard disk space that allows Microsoft Exchange to overwrite transaction log files after the data that the log files contain has been committed to the database. The only reason to enable Circular Logging would be when a hard disk capacity is small or is nearly full.

When circular logging is disabled, every single log file goes into the transactional log database, and no limit exists as to how large that database can get. When circular logging is enabled, however, the transactional log can only grow to one megabyte (1 MB) in size. After that limit has been reached, the first log file is overwritten automatically to keep the transactional log database from growing any larger. The term “circular” arises from the fact that the set of log files starts to “rotate” once the disk space limit is reached, something like a LIFO (last-in, first-out) queue.

Circular logging is commonly used with Exchange native data protection, because in that mode, backups are not made so a detailed transactional log is not necessary. Circular logging is disabled by default in Exchange 2010. That’s because, if circular logging has been enabled and the database becomes corrupted or otherwise compromised, it cannot be completely recovered if data has been added more recently than the time that the last full backup was created.

Use the EAC to configure circular logging for a database

• In the EAC, go to Servers > databases.
• Select the mailbox database you want to configure and click Edit icon.
• Check or uncheck the Enable circular logging checkbox, and then click save.
• If a dismount and mount operation are required, a warning message will appear. Click OK to close the warning message.
  To dismount the database, click More More Options Icon, and then click Dismount.
  Click yes when the warning message appears.
• To mount the database, click More More Options Icon, and then click Mount.
  Click yes when the warning message appears.

Use the Shell to configure circular logging for a database

This example enables circular logging for database DB1

Set-MailboxDatabase DB1 -CircularLoggingEnabled $True

This example disables circular logging for database DB1.

Set-MailboxDatabase DB1 -CircularLoggingEnabled $False