Advantages and disadvantages of decreasing the log checkpoint depth in an Exchange 2000 Server cluster

In Microsoft Exchange Server, the Extensible Storage Engine (ESE) writes storage group database transactions to logs, and then the ESE writes storage group database transactions to the database. The maximum amount of data that the Extensible Storage Engine can write to logs before it writes to the database is known as the log checkpoint depth.

You can decrease the log checkpoint depth setting on an Exchange Server computer in a clustered environment. This decrease causes better failover performance. However, this decrease may cause a performance penalty on disk resources and on CPU resources.

Warning If you use the ADSI Edit snap-in, the LDP utility, or any other LDAP version 3 client, and you incorrectly modify the attributes of Active Directory objects, you can cause serious problems. These problems may require you to reinstall Microsoft Windows 2000 Server, Microsoft Windows Server 2003, Microsoft Exchange 2000 Server, Microsoft Exchange Server 2003, or both Windows and Exchange. Microsoft cannot guarantee that problems that occur if you incorrectly modify Active Directory object attributes can be solved. Modify these attributes at your own risk.
On a computer that is running Microsoft Exchange 2000 Server in a clustered environment, the following behavior may occur:

• An Exchange virtual server may be moved from a node.
• An Exchange virtual server may fail over to another node.

Before the move or the failover, the following behavior occurs in the following order:

1. All transaction logs are written to the database.
2. The Information Store that is on the source node is taken offline.

The more data that there is to be written to the databases, the more time there is for the changeover.

In Exchange 2000 Server, the default log checkpoint depth is 20 megabytes (MB). Therefore, 20 MB of logs may have to be written to the databases before an Information Store shutdown is initiated. Therefore, the time that is required for the Exchange virtual server to move depends on the time that is required for the transaction logs to be written to the databases. By reducing the log checkpoint depth, you can reduce the write timings. By reducing the write timings, you reduce the failover times.

To reduce the checkpoint depth, you must use the Active Directory Service Interfaces (ADSI) Edit utility to change the msExchESEParamCheckpointDepthMax attribute value in the Active Directory directory service. To apply the new settings, you must restart the Exchange Information Store service.

To modify the checkpoint depth, follow these steps:

1. Log on to a computer in the domain that has the Microsoft Windows Support Tools installed.
   
   For additional information about how to install Microsoft Windows 2000 Support Tools, click the following article number to view the article in the Microsoft Knowledge Base:
   301423� How to install the Windows 2000 Support Tools to a Windows 2000 Server-based computer
2. Open a command prompt, and then locate the folder where the support tools are installed. By default, the support tools are installed in the C:\Program Files\Support Tools folder.
3. Type adsiedit.msc, and then press ENTER. By default, the ADSI Edit utility connects to the directory of the domain where you are currently logged on.
4. In the console tree, expand Configuration Container, CN=Configuration, CN=Services, CN=Microsoft Exchange, CN=Your_ Organization_Name, CN=Administrative Groups, CN=Your_Administrative_Group, CN=Servers, CN=Your_Server_Name, CN=Information Store, CN=Your_Storage_Group_Name.
5. Right-click CN=Your_Storage_Group_Name, and then click Properties.
6. In Select a property to view, select msExchESEParamCheckpointDepthMax.
7. In Edit Attribute, type the size you want to set the maximum cache size to. Type the size in bytes. Type the bytes in multiples of 5 MB.
   
   For example, for a checkpoint depth of 5 MB, you must type 5242880. For a checkpoint depth of 10 MB, you must type 10485760. The minimum checkpoint depth is 5 MB. If you type a checkpoint depth that is larger than 20 MB, it will increase Exchange cluster failover times.
8. Quit the ADSI Edit utility.
9. Restart the Exchange Information Store service. To do this, follow these steps:
   1. Click Start, point to Programs, point to Administrative Tools, and then click Services.
   2. Right-click the Exchange Information Store service, and then click Re-start.

Note In an environment that has multiple domain controllers, you must wait for this attribute change to be replicated in Active Directory before you see the changes reflected on the Exchange 2000 Server computer.

A reduction in the log checkpoint depth causes the Exchange Store Engine to write data to the databases more frequently. This behavior may cause disk and CPU performance penalties. Whether this behavior causes these performance penalties depends on your environment. A reduction of the checkpoint depth from 20 MB to 5 MB may cause a penalty of 5 percent on disk and CPU resources.

For additional information about how to monitor uncommitted checkpoint logs, click the following article number to view the article in the Microsoft Knowledge Base: