Q185693: XADM: Spinning Thread in Mad.exe During Routing Recalculation
Article: Q185693
Product(s): Microsoft Exchange
Version(s): winnt:5.0 SP2,5.5,5.5 SP1
Operating System(s):
Keyword(s): exc55sp2fix exc55 exc5sp2 exc55sp1
Last Modified: 06-AUG-2002
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The information in this article applies to:
- Microsoft Exchange Server, versions 5.0 SP2, 5.5, 5.5 SP1
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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
========
The Exchange System Attendant process (Mad.exe) shows sustained, high CPU
utilization in a Performance Monitor chart view. Viewing the individual threads
of Mad.exe in Perfmon, you see that a single thread is maintaining high
utilization. Server performance may appear sluggish (particularly on single
processor systems).
Additionally, the Exchsrvr\Mtadata\Gwartx.mta files likely show a date and time
stamp corresponding to the last restart time of the message transfer agent
(MTA). This time stamp will not be updated over a 24-hour time period, and the
following event may be logged in the Event Viewer:
Event: 5000
Source: MSExchangeSA
Type: Error
Category: General
Recalculation of the routing table is complete. Result: The routing table is
being recalculated.
CAUSE
=====
The routing topology of the Exchange organization exceeds the practical
limitations of the "aggressive pruning" algorithm introduced with MTA
enhancements that were included in 5.5 and 5.0 SP2 (see Microsoft Knowledge Base
article Q176518, XCON: Recalculating Routing Does Not Remove Previously Deleted
Routes). Routing recalculation can take hours, days, or even weeks longer than
it did using the previous algorithm.
RESOLUTION
==========
To resolve this problem, obtain the latest service pack for Exchange Server
version 5.5. For more information, please see the following article in the
Microsoft Knowledge Base:
Q191014 XGEN: How to Obtain the Latest Exchange Server 5.5 Service Pack
Post-5.5 SP1 and 5.0 SP2 versions of the MTA have been compiled that allow the
administrator to use a registry value to toggle between using the old algorithm
and using the new "extra checking\aggressive pruning" algorithm.
The default action of these MTAs, without the registry value set, is to engage
the "extra checking" enhancement.
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.
The fix is a replacement of the Exchange MTA and requires that the following
Windows NT registry value be added:
HKLM\System\CurrentControlSet\Services\MSExchangeMTA\Parameters RID
Consistency Checking : REG_DWORD : 0
To add this registry value:
1. Start Registry Editor (Regedt32.exe).
2. Locate the following key in the registry:
HKEY_LOCAL_MACHINE\System\CurrentControlSet\Services
\MSExchangeMTA\Parameters
3. On the Edit menu, click Add Value and use the following entry:
Value Name: RID Consistency Checking
Data Type: REG_DWORD
Value: 0
NOTE: Spaces and capitalization are important. Setting the registry value to 0
(zero) disables the extra route checking.
4. Quit Registry Editor.
5. Restart all Exchange services.
NOTE: Routing recalulation occurs on only one server in the site. To determine
the current Routing Calculation Server, open the
<organization>\<site>\Configuration\Site Addressing property page
and look at the Routing Calculation Server list box. It is recommended that all
servers be upgraded with the new MTA and registry setting because the Routing
Calculation Server can be easily changed in the Microsoft Exchange Administrator
program. Although routing recalculation is performed by the MTA component,
Ems_rid.dll, this .dll file executes under the system attendant process.
STATUS
======
Microsoft has confirmed this to be a problem in Exchange versions 5.0 SP2, 5.5,
and 5.5 SP1. This problem was first corrected in Exchange Server 5.5 Service
Pack 2.
MORE INFORMATION
================
Article Q176518, explains the purpose of the "aggressive pruning" algorithm. The
purpose is to hasten the removal of deleted routes from the site's routing
recalculation server, thus removing these routes from the site.
The original algorithm basically performs the following:
Searches all local Connectors and starts off with an empty GWART. For each
Connector found, adds the address spaces for the Connectors. If Connected Sites
is set, imports in the remote site's GWART. During this import, removes
duplicated addresses and circular routes.
The "extra checking":
Checks each imported route from the remote GWART. For every hop on the route,
imports the GWART for the site corresponding to that hop, and verifies that the
hop exists in that GWART also.
The time required for extra checking factors exponentially to the number of sites
and routes defined. In very large topologies where there are many routes
defined, the time taken to perform the extra checking can be days or possibly
even weeks.
Additional query words:
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Keywords : exc55sp2fix exc55 exc5sp2 exc55sp1
Technology : kbExchangeSearch kbExchange550 kbZNotKeyword2 kbExchange500SP2 kbExchange550SP1
Version : winnt:5.0 SP2,5.5,5.5 SP1
Issue type : kbbug
Solution Type : kbfix
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