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Q265186: XCON: MTA Fanout Slows on Multiprocessor Servers

Article: Q265186
Product(s): Microsoft Exchange
Version(s): 5.5
Operating System(s): 
Keyword(s): kbenv kbExchange550
Last Modified: 07-AUG-2002

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The information in this article applies to:

- Microsoft Exchange Server, version 5.5 
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IMPORTANT: This article contains information about modifying the registry. Before you 
modify the registry, make sure to back it up and make sure that you understand how to restore 
the registry if a problem occurs. For information about how to back up, restore, and edit the 
registry, click the following article number to view the article in the Microsoft Knowledge Base:

  Q256986 Description of the Microsoft Windows Registry

SYMPTOMS
========

When you run Exchange Server 5.5 on a multiprocessor server, the message
transfer agent (MTA) fanout may slow down or stall. Messages back up in the
private information store but nowhere else. When you try running Performance
Optimizer (Perfwiz.exe), the overall performance of Exchange Server slows down.

CAUSE
=====

This behavior can occur because Performance Optimizer does not properly optimize
the MTA and information store when you run it on multiprocessor servers.
Specifically, it does not allocate enough information store threads to increase
the routing capacity of the MTA. Performance Optimizer also resets any changes
that you make.

RESOLUTION
==========

There are two ways to resolve this behavior.

Run Performance Monitor in Verbose Mode to Modify Thread Counts
---------------------------------------------------------------

To resolve this behavior, run Performance Optimizer in verbose mode (perfwiz -v)
to modify thread counts:

1. At a command prompt, switch to the Exchsrvr\Bin directory, type "perfwiz -v"
  (without the quotation marks), and then press ENTER to start Performance
  Optimizer in verbose mode.

2. In the Microsoft Exchange Performance Optimizer, click Next until you find
  the property page that includes the Users on this server and Users in
  organization boxes. In these boxes, be sure to allocate enough resources to
  handle your work load. If the number of users falls in the high end of a
  range, select the next higher range. Under Memory Usage, do not limit
  Exchange Server memory usage.

3. Click Next until you find the # of background threads box. Note this value
  but do not change it, and then click Next.

4. In the Public and Private Information Store box, increase each of the four
  send and delivery thread values to 8.

5. Click Back to return to the # of background threads box, and then increase
  that value accordingly. For example, if you increase each of the four send
  and delivery thread values from 2 to 8, increase the background threads value
  by 24.

  NOTE: You can make these changes manually in the registry, but these values
  are not visible by default. Running perfwiz -v automatically adds the values
  for you and eliminates any worry about spelling and case sensitivity.

6. Click Next until you find the # of submit/deliver threads box. The MTA uses
  these threads to pass mail off to the information store. Increase this value
  to 8 also; its maximum default setting is 4.

7. On the same page, specify the following values:

  Dispatcher threads: 8
  Kernel threads: 8
  RTS threads: 8
  Transfer threads: 8

  Increasing these values to 8 allows for a larger pipe between the MTA and the
  information store, yielding more efficient clearing of the message backlog
  under high-traffic conditions.

8. Click Next until you find the # of TCP/IP control blocks box. Make sure it is
  not reset to 20 unless that is the appropriate value.

NOTE: Perfwiz -v tries to reset the Transmission Control Protocol (TCP) control
blocks parameter to 20. Compare settings before committing changes.

9. Click Next, click Finish, and then restart services. Monitor the MTA queue to
  the information store to verify that the changes affect the queue.

Modify the Registry
-------------------

WARNING: If you use Registry Editor incorrectly, you may cause serious problems
that may require you to reinstall your operating system. Microsoft cannot
guarantee that you can solve problems that result from using Registry Editor
incorrectly. Use Registry Editor at your own risk.

To resolve this behavior, create or change the following in the Windows NT
registry:

1. Start Registry Editor (Regedt32.exe).

2. Locate and click the following key in the registry:

  HKEY_LOCAL_MACHINE\System\CurrentControlSet\Services\MSExchangeMTA\Parameters

NOTE: The above registry key is one path; it has been wrapped for readability.

3. On the Edit menu, click Add Value, and then add the following registry value:

  Value Name: Allow fuzzy proxy search
  Data Type: REG_DWORD
  Value: 2

NOTE: If this registry value does not exist in the registry, the MTA assumes a
value of 1 for this setting and enables fuzzy proxy searches.

4. Quit Registry Editor.

MORE INFORMATION
================

"Fanout" is the process of placing objects into the various queues.

Verbose mode stops all services and offers options not available in normal mode.
You do not need to analyze hard disks or move files; this procedure presents the
opportunity to change some resource (thread) settings from the defaults.

To view the current settings for Users on this server and Users in organization
without stopping services, at a command prompt, run "perfwiz -r" (without the
quotation marks). You can also use the Perfopt.log file in the Winnt\System32
folder to view any changes that Performance Optimizer makes to the system.

For additional information about MTA fanout, messages in the information store,
and improving MTA network performance, click the article number below to view
the article in the Microsoft Knowledge Base:

  Q176046 XCON: Routing Issues with Microsoft Exchange Server, Version 5.0

  Q159184 XADM: MTA Fails to Deliver Messages with High DS Activity

  Q234280 XCON: Increasing MTA Ability to Pass Mail over Slow Connections

  Q234702 XGEN: MTA Queue to Information Store Processing Slowly

Concerning Knowledge Base article Q234702, note that if you change the public and
private send and deliver threads, you must also check the concurrent XAPI
sessions to make sure that value is set adequately. Otherwise, you may
experience new performance issues and may receive an error message about Event
ID 3120 from the MTA.

Additional query words:

======================================================================
Keywords          : kbenv kbExchange550 
Component         : MTA
Technology        : kbExchangeSearch kbExchange550 kbZNotKeyword2
Version           : :5.5
Issue type        : kbprb

=============================================================================

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