DOCUMENT:Q184823  10-APR-1999  [exchange]
TITLE   :XADM: Bad Schema Index After Exchange 4.0 to 5.5 Upgrade
PRODUCT :Microsoft Exchange
PROD/VER:WinNT:5.5
OPER/SYS:
KEYWORDS:

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The information in this article applies to:

 - Microsoft Exchange Server, version 5.5 
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SYMPTOMS
========

Users experience Exchange service outages from roughly 20 seconds to 4 minutes
long sporadically throughout the day. Threads in Dsamain.exe may spike to 100
percent.

CAUSE
=====

Under Microsoft Exchange Server 4.0, the schema index for the directory service
defaults to 0. This amounts to a flat scan for every directory service request.
The algorithm has changed significantly from 4.0 to 5.5 for the database
retrieval mechanism, including improved caching. Under version 5.5, a flat scan
has a significant performance cost and hence the index defaults to 1 by design.
However, when you install version 5.5 in a version 4.0 environment or upgrade
4.0 to 5.5, this value remains 0 and causes the server outage described above.

STATUS
======

Microsoft has confirmed this to be a problem in Microsoft Exchange Server
version 5.5. This problem has been corrected in the latest U.S. Service Pack for
Microsoft Exchange Server version 5.5. For information about obtaining the
Service Pack, query on the following word in the Microsoft Knowledge Base
(without the spaces):

   S E R V P A C K


WORKAROUND
==========

To work around this problem, set the directory service schema index to 1 for
Exchange Server 5.5 computers in a mixed 4.0/5.5 environment. To do this,
perform the following steps:

WARNING: Using the raw mode of the Exchange Administrator program (admin /r)
incorrectly can cause serious problems that may require you to reinstall
Microsoft Windows NT Server and/or Microsoft Exchange Server. Microsoft cannot
guarantee that problems resulting from the incorrect use of raw mode can be
solved. Use raw mode at your own risk.

1. Start the Exchange Administrator program in raw mode by typing the following
   at a command prompt:

   admin /r

2. On the View menu, click Raw Directory.

3. Select the Schema object in the Exchange Administrator hierarchy. This is
   located under the site name.

4. Open the Properties window for the Directory Name schema object.

5. In the Object Attribute list, click Search-Flags.

6. Change the Edit Value to 1. Then select Set.

7. Restart the directory service.

NOTE: This change must be made on one server within each site experiencing the
problem. This change will be replicated to all the servers within the site.

Additional query words: dsamain msexchangeds RPC Requests high perfmon.exe perfmon slow

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Keywords          :  
Technology        : kbExchangeSearch kbExchange550 kbZNotKeyword2
Version           : WinNT:5.5
Issue type        : kbbug
Solution Type     : kbfix

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