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Circular logging is enabled

[This topic is intended to address a specific issue called out by the Exchange Server Analyzer Tool. You should apply it only to systems that have had the Exchange Server Analyzer Tool run against them and are experiencing that specific issue. The Exchange Server Analyzer Tool, available as a free download, remotely collects configuration data from each server in the topology and automatically analyzes the data. The resulting report details important configuration issues, potential problems, and nondefault product settings. By following these recommendations, you can achieve better performance, scalability, reliability, and uptime. For more information about the tool or to download the latest versions, see "Microsoft Exchange Analyzers" at http://go.microsoft.com/fwlink/?linkid=34707.]  

Topic Last Modified: 2007-01-05

The Microsoft® Exchange Server Analyzer Tool queries the Active Directory® directory service to determine the value for the msExchESEParamCircularLog attribute of each storage group on the Exchange server. A value of 1 indicates that circular logging is enabled for the storage group. A value of 2 indicates that circular logging is not enabled for the storage group. In addition, the Exchange Server Analyzer also queries Active Directory to determine the count of the entries listed in the homeMDBBL attribute of each mailbox store. The count of this attribute represents the number of mailboxes on the mailbox store.

The Exchange Server Analyzer also queries the Exchange_Server Microsoft Windows® Management Instrumentation (WMI) class in the root\MicrosoftExchangeV2 namespace to determine the value for the IsFrontEndServer key. A value of True indicates the Exchange Server computer is a front-end server. A value of False indicates that the Exchange Server computer is not a front-end server.

If the Exchange Server Analyzer finds the value for the msExchESEParamCircularLog attribute set to 1, the value for the IsFrontEndServer key set to False, and the value of the homeMDBBL attribute to be greater than 20, a warning is displayed.

This combination of values indicates that circular logging is enabled on a mailbox server that contains more than 20 mailboxes. In the standard transaction logging used by Exchange 2000 Server, Exchange Server 2003, and Exchange Server 2007, each database transaction in a storage group is written to a log file and then to the database. When a log file reaches a certain size, it is renamed and a new log file is created. Over time, this results in a set of a log files. If there is a crash, you can recover the transactions by replaying the data from these log files into the database.

Circular logging overwrites and reuses the first log file after the data it contains has been written to the database. In Exchange 2000 Server, Exchange Server 2003, and Exchange Server 2007, circular logging is disabled by default. By enabling it, you reduce drive storage space requirements, but without complete transaction log files, you cannot recover anything more recent than the last full backup. Therefore, in a normal production environment, circular logging is not recommended.

  1. Open Exchange System Manager.

  2. Expand Servers, and then expand the server you want to modify.

  3. Right-click the storage group that you want to change, and then click Properties.

  4. In the Properties dialog box, clear the Enable circular logging check box.

  5. Click OK to save the setting.

  6. Close Exchange System Manager and restart the Microsoft Exchange Information Store service for the change to take effect.

  1. Open Exchange Management Console.

  2. Expand Server Configuration, and then expand the server you want to modify.

  3. Right-click the storage group that you want to change, and then click Properties.

  4. In the Properties dialog box, clear the Enable circular logging check box.

  5. Click OK to save the setting.

  6. Close Exchange Management Console and restart the Microsoft Exchange Information Store service for the change to take effect.

  1. The following code is an example of the Set-StorageGroup command that disables circular logging for the 'MyStorageGroup' storage group.

Set-StorageGroup -Identity MyStorageGroup -CircularLoggingEnabled $false
 
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