XADM: How to Modify the Circular Logging Setting

This article describes how to modify the circular logging setting on a Microsoft Exchange 2000 Server computer. The following topics are discussed:

• Description of circular logging
• Enabling or disabling circular logging

Description of Circular Logging

In the standard transaction logging used by Exchange 2000 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 2000 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, in a normal production environment, circular logging is not recommended.

How to Enable or Disable Circular Logging

Exchange 2000 Server supports multiple databases and storage groups on the same server. You can create up to four storage groups on a server and each storage group can contain up to five databases, for a maximum of 20 databases on a single server. Each storage group is controlled by a separate instance of the Extensible Storage Engine (ESE). Therefore, each storage group shares the same set of log files. As a result, circular logging is enabled or disabled for a particular storage group, not for a particular database.

To enable or disable circular logging:

1. Click Start, point to Programs, point to Microsoft Exchange, and then click System Manager.
2. If the Administrative Groups branch exists in the left pane, expand it, expand the appropriate administrative group's branch, expand the Servers branch, and then expand the appropriate server's branch. If the Administrative Groups branch does not exist, expand the Servers branch in the left pane, and then expand the appropriate server's branch. To expand a branch, double-click the branch or click the plus sign (+) to the left of the branch.
3. Right-click the storage group you want, and then click Properties.
4. To enable circular logging, click to select the Enable circular logging check box, and then click OK. When you are prompted to continue, click Yes.
   
   To disable circular logging, click to clear the Enable circular logging check box, and then click OK.
5. Restart the information store. To do so:
   1. Click Start, point to Programs, point to Administrative Tools, and then click Services.
   2. Click Microsoft Exchange Information Store in the right pane, and then on the Action menu, click Restart. If a dialog box appears stating that additional services will be restarted, click Yes.
   NOTE: The information store must be restarted because when it starts, it reads configuration information from Microsoft Windows 2000 Active Directory. The Active Directory attribute associated with the circular logging setting is called MSExchESEParamCircularLog. When circular logging is enabled, this attribute is set to 1. When circular logging is disabled, it is set to 0.