In this article, we present an overview of the Microsoft Exchange circular logging concept. We also provide you with the instructions on enabling or disabling this feature on Microsoft Exchange Servers editions 2003-2016.
Table of Contents
If you would like to find out more about MS Exchange backup and recovery, please refer to our corresponding guide.
Further reading MS Exchange Server Backup and Recovery Guide
Why You Need Circular Logging on Exchange Server?
Microsoft Exchange Server traditionally uses a write-ahead approach to commit new data to the database. That means that when you, for instance, create a new email, data transactions are written to the log file. Afterward, MS Exchange commits this log file to the database and then marks it as recyclable.
Since committed log files won't be deleted automatically, you can recover the database in the most recent state after a failure of any kind. To do so, you simply restore the last database backup with the corresponding log files. The Exchange server applies each of them sequentially, thus creating data transactions history from scratch. These log files are only deleted after a successful full database backup, or by enabling the Circular Logging feature.
Circular Logging allows you to keep the storage space consumed by log files as low as possible by keeping only a few log files on the disk. It does this by overwriting older files with new transactions. However, it also leaves you with no logs-based recovery features.
Using Circular Logging, you are only able to restore a Microsoft Exchange database using point-in-time backups. Moreover, you can only create FULL database backups, since incremental ones rely on the logs mechanism.
Enabling and Disabling Circular Logs on Exchange Server
Now, let’s explain how to enable or disable circular logging enabling on popular versions of Microsoft Exchange Server.
1Open the System Manager tool.
2Navigate to the storage group you need to change under the Server item.
3Choose Properties in the context menu of the storage group, then use the Enable Circular Logging check box to enable or disable the feature. Confirm your selection by clicking OK and then Yes.
4Now you need to restart Exchange Information Store service. Use the Services system snap-in: Find the Microsoft Exchange Information Store service and select Restart in its context menu.
1Run Exchange Management Console.
2Find Server Configuration in the navigation tree and click Mailbox. Find the storage group you need to change settings for.
3Click Properties in the context menu of the selected storage group, then use the Enable Circular Logging check box to enable or disable the feature. Confirm your selection by clicking OK.
4Restart Exchange Information Store service, or do an unmount and mount for all databases in the storage group so that changes take effect. Restarting the service is easier, to do so, open the Services snap-in, find the Microsoft Exchange Information Store service and select Restart in its context menu.
1Open Exchange Management Console and navigate to the Mailbox role in Organization Configuration.
2Select the target database on the Database Management tab, click Properties below the database name.
3Go to the Maintenance tab and use the Enable circular logging check box to enable or disable the feature; click OK and restart Microsoft Exchange Information Store service the same way as explained above for Exchange 2007.
There is also a simpler way using Exchange Management Shell (EMS):
Set-MailboxDatabase -Identity "database_name" -CircularLoggingEnabled $false
Replace “database_name” with target DB name, and use “true” or “false” to enable or disable the feature. Do not forget to run Exchange Management Shell with elevated privileges.
1Run Exchange Admin Center and go to Databases under the Servers scope.
2Select the desired mailbox database and click the edit icon.
3Use the Enable Circular Logging check box to enable or disable the feature. Then click Save and restart Microsoft Exchange Information Store service as we described earlier.
The EMS commandlet is also available for use in Exchange 2013. See the steps above from Exchange 2010 section.
1Start Exchange Admin Center and go to the Databases tab.
2Double-click the desired database and click on the maintenance menu.
3Use the Enable Circular Logging check box to enable or disable the feature. Then you need to unmount and mount the database to take changes into effect.
The EMS commandlet is also available for use in Exchange 2016. See the steps above from the Exchange 2010 section.
Issues with Circular Logging
The Exchange logging mechanism, when combined with Windows Volume Shadow Copy (VSS), allows you to create a database hot backup without user interruption. Therefore, you may experience difficulties with Exchange backup if VSS is not properly configured. In some cases, you will even get an error in case of a backup of other VSS-enabled backups on the same server. The reason is that most backup tools use the Windows VSS writer feature
VSS troubleshooting starts with checking the VSS writers status using the following command:
vssadmin list writers
If you get an error message, it may be the result of a problem with the VSS mechanism. Check the source writer status and then use this guide to find additional details
In this article, we explained how to enable or disable the Circular Logging feature on various editions of MS Exchange servers, starting with Exchange 2003. Use this feature carefully and remember that you cannot perform incremental backups when Circular Logging is enabled.