DOCUMENT:Q230691  11-JUN-2002  [exchange]
TITLE   :XADM: Space Tree Fragmentation Degrades Server Performance
PRODUCT :Microsoft Exchange
PROD/VER:winnt:5.5
OPER/SYS:
KEYWORDS:exc55 EXC55SP3Fix

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The information in this article applies to:

 - Microsoft Exchange Server, version 5.5, on platform(s):
    - the hardware: DEC Alpha 
    - the hardware: Intel x86 
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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
==========

To resolve this problem, obtain the latest service pack for Exchange Server
version 5.5. For additional information, please see the following article in the
Microsoft Knowledge Base:

   Q191014 XGEN: How to Obtain the Latest Exchange Server 5.5 Service Pack

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

Component: JET

+-------------------------+
| File name | Version     | 
+-------------------------+
| Ese.dll   | 5.5.2650.16 | 
+-------------------------+



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
version 5.5. This problem was first corrected in Exchange Server 5.5 Service
Pack 3.

Additional query words: JET slow hang perf

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Keywords          : exc55 EXC55SP3Fix 
Technology        : kbExchangeSearch kbZNotKeyword2
Version           : winnt:5.5
Issue type        : kbbug
Solution Type     : kbfix

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