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Initial Memory Percentage

The following is tip #5 from ""25 Exchange 2003 Tips in 25 minutes"

The following is Tip #5 from "25 Exchange 2003 Tips in 25 minutes." This content is excerpted from Scott Schnoll's book, "Microsoft Exchange Server 2003 Distilled," brought to you by © (2004) Pearson Education, Inc. Publishing as Addison-Wesley Professional. Return to the main page for more tips on this topic.


It is important to monitor virtual memory on Exchange servers for two reasons: (1) the more virtual memory available, the greater the load that can be handled; and (2) performance problems can occur (especially on Exchange clusters) when virtual memory becomes too fragmented. When virtual memory becomes too fragmented, Exchange logs the following event in the Application event log.

Event Type: Error
Event Source: MSExchangeIS
Event Category: Performance
Event ID: 9582
Date: 10/10/2003
Time: 3:42:38
User: N/A
Computer: EX2K3
Description: The virtual memory necessary to run your Exchange server is fragmented in such a way that normal operation may begin to fail. It is highly recommended that you restart all Exchange services to correct this issue.

As this event log entry indicates, restarting all Exchange services was needed in order to correct the problem. If this happened regularly, you ended up restarting Exchange frequently, and both your users and management probably wondered why their e-mail server was so unreliable.

To combat the virtual memory fragmentation problem, Microsoft introduced the following registry entry and recommended value in Exchange 2000 that hard-coded Exchange's initial memory allocation to 10% of the total amount of physical memory in the system.

Location:
HKLM\System\CurrentControlSet\Services\MSExchangeIS\ParametersSystem
Value: Initial Memory Percentage
Type: REG_DWORD
Value Data: 0xa (hex)

By starting out with this initial allocation and then growing from there, virtual memory fragmentation would not occur as often. Exchange 2003 includes support for special startup switches in Windows 2000 Advanced Server and Windows Server 2003 that help reduce virtual memory fragmentation, and Microsoft made additional changes to help prevent virtual memory fragmentation in Exchange clusters. As a result, the Initial Memory Percentage registry value is no longer needed. Moreover, because it does not work on an Exchange 2003 server, you should remove this value from all Exchange 2000 servers prior to upgrading to Exchange 2003.


Get more "25 Exchange 2003 Tips in 25 minutes." Return to the main page.

About the author: Scott Schnoll, an Expert on SearchExchange.com, is an MCT, MCSA and a long-time Microsoft Most Valuable Professional (MVP).

In addition to writing "Microsoft Exchange Server 2003 Distilled," he is a co-author of the upcoming "Exchange 2003 Resource Kit from Microsoft Press" and lead author for "Exchange 2000 Server: The Complete Reference."

Scott has written numerous articles for Exchange & Outlook Magazine, and is a regular speaker at Microsoft conferences, including MEC and TechEd, as well as industry conferences such as Comdex and MCP TechMentor, where he covers topics such as Exchange, clustering, Internet Information Services and security.

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