XADM: Space Tree Fragmentation in Exchange Database Engine Can Degrade Server Performance

ID: Q230691

The information in this article applies to:

Microsoft Exchange Server, version 5.5
on the following platforms: Alpha, x86

SYMPTOMS

Messages begin backing up and/or moving out slowly in the private information store queue in the Microsoft Exchange Message Transfer Agent (MTA).
The information store process CPU use (as seen by using Windows NT Performance Monitor) begins to increase as the length of the MTA queue increases.
A given number of threads belonging to the information store process Store.exe, (as seen by using Windows NT Performance Monitor) seem to be running at a high CPU percentage for a long period of time (that is, more than 30 percent).

CAUSE

Available space in the Exchange Server information store database is in the form of a list of pages that can be used to store new data. The available space is called a space tree. The space tree is held as binary tree that is searched whenever a block of new data needs to be added to the database.

The problems in the "Symptoms" section are caused when the space tree becomes very fragmented, causing the size of the binary tree to grow very large. This large space tree causes massive I/O when navigating through the binary tree looking for space. As a result, the performance of the server degrades as more and more information store threads navigate the space tree.

RESOLUTION

A supported fix that corrects this problem is now available from Microsoft, but it has not been fully regression tested and should be applied only to systems experiencing this specific problem. If you are not severely affected by this specific problem, Microsoft recommends that you wait for the next Microsoft Exchange Server version 5.5 service pack that contains this fix.

To resolve this problem immediately, contact Microsoft Product Support Services to obtain the fix. For a complete list of Microsoft Product Support Services phone numbers and information on support costs, please go to the following address on the World Wide Web:

http://www.microsoft.com/support/supportnet/overview/overview.asp

The English version of this fix should have the following file attributes or later:

Component: JET

File name	Version
Ese.dll	5.5.2608.0

This hotfix has been posted to the following Internet location as Psp2esea.zip and Psp2esei.zip:

ftp://ftp.microsoft.com/bussys/exchange/exchange-public/fixes/Eng/Exchg5.5/PostSP2/ese-fix/

NOTE: If this product was already installed on your computer when you purchased it from the Original Equipment Manufacturer (OEM) and you need this fix, please call the Pay Per Incident number listed on the above Web site. If you contact Microsoft to obtain this fix, and if it is determined that you only require the fix you requested, no fee will be charged. However, if you request additional technical support, and if your no-charge technical support period has expired, or if you are not eligible for standard no-charge technical support, you may be charged a non-refundable fee.

For more information about eligibility for no-charge technical support, see the following article in the Microsoft Knowledge Base:

Q154871 Determining If You Are Eligible for No-Charge Technical Support

WORKAROUND

An offline defragmentation (eseutil /d ispriv |ispub) of the database will shrink the size of the space tree, and provide relief until the time the fragmentation builds up once more in the space tree.

STATUS

Microsoft has confirmed this to be a problem in Microsoft Exchange Server 5.5.

Additional query words: JET slow hang perf


Keywords          : 
Version           : winnt:5.5
Platform          : winnt 
Issue type        : kbbug

Last Reviewed: August 8, 1999