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Increase Transaction Log Log Buffers Setting

[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]  

Topic Last Modified: 2005-11-18

The Microsoft® Exchange Server Analyzer Tool has determined that the number of log buffers on your server is too low. The tool has detected that the Database (Information Store Instance)\Log Record Stalls/sec value for your server is greater than 10 stalls per second. A value greater than 10 indicates that there is a backup writing to the transaction log. This situation can occur because the transaction log drive is beyond its throughput capacity, or because the log buffers are set too low.

Log write I/O's are sequential and single threaded, so the latency on log I/O is often a bottleneck to the system. Log I/O’s are written to the log buffers first, and then the buffer is cleared by either a non-lazy commit or a capacity commit. A non-lazy commit means that the log buffer is written to the disk immediately. A capacity commit means that the log buffer is written to the disk when the buffer becomes full.

Increasing the log buffer size reduces the frequency of capacity flushes, increases the log write size, and subsequently reduces the overall log write latency. Reducing the log I/O write latency is a significant way to improve the performance/scalability of the Exchange deployment.

The general recommendation is to increase the buffer size to the maximum of 9,000 for Exchange Server 2003 and to 512 for Exchange 2000 Server.


If you incorrectly modify the attributes of Active Directory objects when you use ADSI Edit, the LDP tool, or another LDAP version 3 client, you may cause serious problems. These problems may require that you reinstall Microsoft Windows Server™ 2003, Exchange Server 2003, or both. Modify Active Directory object attributes at your own risk.

To correct this warning

  1. Start ADSI Edit.

  2. Double-click the Configuration container, expand CN=Services, expand CN=Microsoft Exchange, and then expand CN=ExchangeOrganizationName.

  3. Expand CN=Administrative Groups, expand CN=AdministrativeGroupName, and then expand CN=Servers.

  4. Expand CN=ExchangeServerName, expand CN=InformationStore, right-click CN=Storage Group Name, and then click Properties.

  5. In the Select a property to view box, click msExchESEParamLogBuffers.

  6. In the Edit Attribute box, type the appropriate value for your version of Exchange for msExchESEParamLogBuffers, and then click Set.


    For computers that are running Exchange 2000 Server, Exchange 2000 Server Service Pack 1 (SP1), Exchange 2000 Server SP2, or Exchange 2000 SP3, set the value to 512. For computers that are running the original release version of Exchange Server 2003 or Exchange Server 2003 SP1, set the value to 9,000.

  7. Click Apply, and then click OK.

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