Q234702: XGEN: MTA Queue to Information Store Processing Slowly

Article: Q234702
Product(s): Microsoft Exchange
Version(s): winnt:5.5
Operating System(s): 
Keyword(s): exc55
Last Modified: 18-AUG-1999

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The information in this article applies to:

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

If you view the message transfer agent (MTA) queues by means of the Exchange
Server Administrator program or Performance Monitor, the information store
(either public or private, or both) may exhibit a backlog in the message queue.
This behavior is often evident on servers with two to four processors and 800
megabytes (MB) or more of RAM. Manual tuning of the registry allows full use of
hardware resources and more efficient clearing of the message backlog under
high-traffic conditions.

CAUSE
=====

Because computer hardware has become less expensive, many companies use more RAM
and processors on Exchange Server computers to increase performance. However,
Performance Optimizer (Perfwiz.exe) does not automatically tune some registry
parameters to fully use all of these hardware resources.

You can confirm this behavior in Performance Monitor through the counters
specified below:

  Object: MSExchangeMTA Connections
  Counter: Queue Length
  Instance: Microsoft Private MDB
  Description: Queue Length is the number of outstanding messages queued for
  transfer to the entity.

  Object: Private Information Store
  Counter: Receive Queue Size
  Description: Receive Queue Size is the number of messages in the private
  information store's receive queue.

If these two values are more or less equivalent, the information store is not
effectively processing the inbound transactions from the MTA, and the bottleneck
is a result of the information store's inability to handle these transactions in
a timely manner. Also, the MTA may not be handing off mail quickly enough for
the information store. In addition, MTA and information store CPU use (as
monitored by Performance Monitor) may be low on the affected server.

WORKAROUND
==========

To work around this problem, increase resource (thread) settings from the
defaults:

1. From a command prompt go to the Exchsrvr\Bin directory, and run "perfwiz -v"
  to start Performance Optimizer in verbose mode. 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. In the Microsoft
  Exchange Performance Optimizer property page, in the "Users on this server"
  and "Users in organization" areas, be sure you allocate enough resources to
  handle your work load. If your number of users falls in the high end of a
  range, select the next (higher) range. In the Memory Usage area, don't limit
  Exchange Server memory usage.

  To view the current settings without stopping services, at a command prompt,
  run "perfwiz -r". You can also use the Perfopt.log file in the Winnt\System32
  folder to view any changes that Performance Optimizer makes to the system.

2. In Performance Optimizer, click Next until the "# of background threads"
  property page is displayed. Note this value, but don't change it. Click Next.

3. In the Public and Private Information Store property page, increase each of
  the four send and delivery thread values to 8.

4. Click Back to move back to the "# of background threads" property page, and
  increase that value accordingly. For example, if you increased each of the
  four send and delivery thread values from a default setting of 2 to 8 (by 6
  threads each) in step 3, then in the "# of background threads" property page
  increase the background threads value by a total of 24.

  You can make these changes manually to the registry, but these values are not
  visible by default. Running "perfwiz -v" automatically adds these values for
  you and eliminates any worry about the spelling or case sensitivity of a
  value.

5. Click Next until the "# of submit/deliver threads" property page is
  displayed. The MTA uses these threads to pass mail off to the information
  store. Increase this value to 8 also; its maximum default setting is 3.

6. Click Next, click Finish, and then restart services. Monitor the MTA queue to
  the information store to verify whether the changes have any effect on the
  queue.

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

For additional information about this problem, click the article numbers below to
view the articles in the Microsoft Knowledge Base:

  Q230691 XADM: Space Tree Fragmentation in Exchange Database Engine Can
  Degrade Server Performance

  Q195006 XADM: Resource Failure Error on Computers with More Than 800 MB of RAM

Additional query words:

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Keywords          : exc55 
Technology        : kbExchangeSearch kbExchange550 kbZNotKeyword2
Version           : winnt:5.5
Issue type        : kbprb

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