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Q158590: XCON: Delivery Restrictions Max CPU and Slow Down Msg Delivery

Article: Q158590
Product(s): Microsoft Exchange
Version(s): 4.0,5.0
Operating System(s): 
Keyword(s): 
Last Modified: 18-FEB-2002

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The information in this article applies to:

- Microsoft Exchange Server, versions 4.0, 5.0 
-------------------------------------------------------------------------------

SYMPTOMS
========

During an extended period of time the following behavior might be seen on an
affected Microsoft Exchange Server computer:

Performance monitor counters
----------------------------

- MTA Work Queue: 2000.

- Messages/Sec: 0,1.

- Message Bytes/Sec: 500.

- Directory Lookups/sec: 30.

- The MTAs and DS combined CPU is nearly 100%.

- Looking at the MTA queues using the Microsoft Exchange Server Administrative
  program does not show any items in the queues.

- The MTADATA contains more than 2000 DB*.DAT files.

- Message delivery is very slow.

Note that these results are examples and may vary from those you encounter on
your computer.


CAUSE
=====

Access to a connector such as the Internet Mail Connector (IMC), located on the
affected server, is limited using distribution lists (DLs). Due to this
restriction, transferred messages have to be checked against this access
limitation and the DLs have to be expanded. Depending on the size and the
nesting level of the DLs, this may cause a considerable performance degradation.

STATUS
======

Microsoft has confirmed this to be a problem in Microsoft Exchange versions 4.0
and 5.0. This problem was corrected in the latest Microsoft Exchange Server 4.0
and 5.0 U.S. Service Packs. For information on 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
==========

1. Do not restrict access to connectors such as the IMC.

2. Do not use DLs to restrict access to connectors such as the IMC.

3. Increase the memory and/or number of processors on the affected computer.

4. Introduce a separate computer and operate the connector in question from
  there.

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

Using DLs to restrict access to connectors is very CPU intensive, even though a
dedicated HUB Server might be used to operate connectors from. As a result, the
faster the computer and the more memory it has, the faster it will be able to
process mail. Even after applying the fix, Microsoft strongly suggests that you
consider adding more memory and/or processors to the computer in question.
Together with the fix described in this article a new registry value is
introduced

  DL Member Cache Size <REG_DWORD>

which can be found under

  H_KEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services
     \MSExchangeMTA\Parameters

This value limits the cache size to be used for DL-Members. This new entry
defaults to a value of 15000.


Installation
------------

1. Stop the MSExchangeMTA service.

2. Stop the MSExchangeIMC service.

3. Backup the following files from the <path>\exchsrvr\bin directory by
  renaming them or copying them to another location:

  Emsmta.exe
  Mtacheck.exe
  Mmiext.dll
  Saalog.dll
  Ems_rid.dll
  P2.xv2
  Address.dll

4. Backup the following file from the \<Path>\Exchsrvr\Mtadata directory
  by renaming it or copying it to another location:

  P2.xv2

5. Backup the following file from the
  \<Path>\Exchsrvr\Connect\Msexcimc\Bin directory by renaming it, or
  copying it to another location:

  Address.dll

6. Copy Emsmta.exe, Mtacheck.exe, Mmiext.dll, Saalog.dll, Ems_rid.dll, P2.xv2,
  and Address.dll to the \<Path>\Exchsrvr\Bin directory.

7. Copy P2.xv2 to the \<Path>\Exchsrvr\Mtadata directory.

8. Copy Address.dll to the \<Path>\Exchsrvr\Exchsrvr\Connect\Msexcimc\Bin
  directory.

9. Restart the MSExchangeMTA, MSExchangeIMC, and any additional service possibly
  stopped in steps 1 and 2.

Additional query words: Distribution List Directory look ups MTA Work Queue

======================================================================
Keywords          :  
Technology        : kbExchangeSearch kbExchange500 kbExchange400 kbZNotKeyword2
Version           : :4.0,5.0
Issue type        : kbbug
Solution Type     : kbfix

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

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