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Maximum Number of Open Tables

The following is tip #7 from "25 Exchange 2003 Tips in 25 minutes"

The following is Tip #7 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.

Although it typically provided little bang for the buck, another way to combat memory fragmentation and allocation issues in Exchange 2000 was to reduce the maximum number of open tables that can be used by Exchange. Exchange 2000 cached data about folders that were not currently accessed, a behavior that in some cases contributed to virtual memory fragmentation. To reduce the cache's impact on virtual memory fragmentation, the msExchESEParamMaxOpenTables attribute in Active Directory would be lowered. Typically this change was made only at the direction of Microsoft PSS; however, it was a documented value, so many administrators have made this change. Certainly you'll want to check your own storage groups to see if the value exists. It was often used in tandem with the /3GB switch in the Windows BOOT.INI file, so it's a pretty safe bet that if you are using /3GB, you probably also have this value set.

msExchESEParamMaxOpenTables is an attribute of storage groups. The recommended value for this attribute also changed periodically throughout the life of Exchange 2000. In Service Pack 2, the default value was automatically set to 42500 on four-way systems and 85000 on eight way systems. In Service Pack 3, this was changed to 13800 and 27600, respectively. If you do find a value set for msExchESEParamMaxOpen Tables on any Exchange 2000 storage group, regardless of its value you will want to return the value for this attribute back to <Not Set > 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, 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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