Topic Last Modified: 2006-03-27
The Microsoft® Exchange Server Analyzer Tool queries the Active Directory® directory service to determine the value configured for the circular logging (msExchESEParamCircularLog) attribute. If the Exchange Server Analyzer finds that this attribute is configured with a value of 0, a warning is displayed.
A value of 1 for the msExchESEParamCircularLog attribute indicates that circular logging is enabled. A value of 0 for the msExchESEParamCircularLog attribute indicates that circular logging is disabled.
In the standard transaction logging used by Exchange Server, 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 Server, 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, on production servers that contain mailbox or public folder data, circular logging is not recommended. However, on front-end Exchange servers that do not have mailboxes or public folders, the only messages that are committed are non-delivery reports (NDRs); therefore, there is no need to keep the transaction files for these servers, nor is there much reason to back up these servers. Enabling circular logging on front-end servers allows the transaction log files to be overwritten and to never exceed 20 MB of data.
To enable circular logging
In Exchange System Manager, expand Servers, and then expand an Exchange server.
Right-click the storage group on which you want to enable circular logging, and select Properties. The storage group properties dialog box will appear.
Select the Enable circular logging check box, and then click OK to save the changes.
Exit Exchange System Manager and restart the Microsoft Exchange Information Store for the change to take effect.
For more information about circular logging, see the following Microsoft Knowledge Base articles:
- 258470, "XADM: How to Modify the Circular Logging Setting"
- 147524, "XADM: How Circular Logging Affects the Use of
Transaction Logs" (http://go.microsoft.com/fwlink/?LinkId=3052&kbid=147524)
- 296788, "Offline Backup and Restoration Procedures for
- 314605, "HOW TO: Turn On or Turn Off Circular Logging in
Exchange 2000 Server" (http://go.microsoft.com/fwlink/?LinkId=3052&kbid=314605)