We are going to overview the Exchange Circular Logging concept and show how you can enable or disable this feature on Microsoft Exchange Servers editions 2003-2016.
Table of Contents
Why Use 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 example, create the new email, data transactions are being written to the log file. Afterwards, MS Exchange will commit this log file to the database and then mark it as recyclable.
Since committed log files won't be deleted automatically, you are able to recover the database in the most recent state after the failure of any kind: you just restore the last database backup with the corresponding log files. The Exchange server applies each of them consequently, thus creating data transactions history from scratch. These log files are only deleted after successful full database backup, or by enabling the Circular Logging feature.
Circular Logging allows you to maintain storage space consumed as low as possible by keeping only a few log files on the disk. It just overwrites older files with new transactions. But it leaves you with no logs-based recovery features.
Using Circular Logging, you are only allowed to restore the database using point-in-time backups. Moreover, you can only create FULL database backups, since incremental ones rely on logs mechanism.
Enabling and Disabling Circular Logs on Exchange Server
Now let us summarise circular logging enabling/disabling manuals for popular versions of Microsoft Exchange Server.
- Open System Manager tool.
- Navigate to the storage group you need to change under the Server item.
- Choose 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.
- Now you need to restart Exchange Information Store service. Use Services system snap-in: find Microsoft Exchange Information Store service and select Restart in its context menu.
- Run Exchange Management Console.
- Find Server Configuration in the navigation tree and click Mailbox. Find the storage group you need to change settings for.
- Click Properties in the context menu of selected storage group, then use the Enable Circular Logging check box to enable or disable the feature. Confirm your selection by clicking OK.
- Restart Exchange Information Store service, or do unmount and mount for all databases in the storage group to take changes into effect. Restarting the service is easier, so open Services snap-in, find Microsoft Exchange Information Store service and select Restart in its context menu.
- Open Exchange Management Console and navigate to the Mailbox role in Organization Configuration.
- Select target database on the Database Management tab, click Properties below the database name.
- Go 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 we did it 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.
- Run Exchange Admin Center and go to Databases under the Servers scope.
- Select desired mailbox database and click the edit icon.
- Use 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.
EMS commandlet is also available - use Exchange 2010 section as an example.
- Start Exchange Admin Center and go to the Databases tab.
- Double-click the desired database and click on the maintenance menu.
- Use 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.
EMS commandline is also available - use Exchange 2010 section as an example.
Issues with Circular Logging
Exchange logging mechanism combined with Windows Volume Shadow Copy (VSS) allows you to create a database hot backup without user interruption. So you may experience difficulties with Exchange backup if VSS is not all right. In some cases you will even get an error in case of a backup of other VSS-enabled backups on the same server. This is because most backup tools use Windows VSS writer feature.
VSS troubleshooting starts from checking VSS writers status using the following command:
vssadmin list writers
If you get an error message that may be produced by the VSS mechanism - check the source writer status and then use this guide for additional details.
Now you know how to enable or disable the Circular Logging feature on the various editions of MS Exchange servers starting from Exchange 2003. Use this feature carefully and remember that you can not perform incremental backups when Circular Logging is enabled.