Article ID: 813814 - Last Review: February 21, 2007 - Revision: 8.3

Exchange networking performance is very slow

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SYMPTOMS

The amount of mail that passes through your Exchange server may substantially decrease, and all network-related functions on your Exchange server may also slow down. Also, the network utilization percentage in Task Manager may be as high as 99 percent.

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CAUSE

This problem may occur in Exchange environments that include a large number of Active Directory directory service domains in a single Exchange 2000 Server organization. Additionally, this problem may occur in a highly distributed environment that has a large number of administrative groups.

Note A "large" number of domains or administrative groups is more than 100 domains or administrative groups.

For each domain that participates in an Exchange organization, the Exchange Recipient Update Service (RUS) must add Access Control Entries (ACEs) to the Access Control Lists (ACLs) of several Active Directory objects. As the number of ACEs increases, the size of the ACL for an object grows. If the total size of an Active Directory object's attributes including the ACL exceeds 32,768 bytes, the Exchange DsAccess component cannot cache that attribute.

Note DsAccess provides a shared memory caching warehouse of directory information to be used by several Exchange components. This reduces the number of queries that go directly to the Windows 2000 Active Directory, and reduces the cost overhead that is associated with direct access to the Active Directory.

If the DsAccess component cannot cache the object's attributes, the Exchange server must now contact a domain controller or a global catalog server to retrieve the attributes. This causes a great deal of network utilization that can be further increased when the data is requested frequently, as is the case with public folder data or when routing e-mail.

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RESOLUTION

Cumulative Rollup Information

To resolve this problem, obtain the September 2003 Exchange 2000 Server Post-Service Pack 3 (SP3) Rollup. For more information, click the following article number to view the article in the Microsoft Knowledge Base:

824282 (http://support.microsoft.com/kb/824282/ ) September 2003 Exchange 2000 Server Post-Service Pack 3 Rollup

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Hotfix Information

A supported hotfix is available from Microsoft. However, this hotfix is intended to correct only the problem that is described in this article. Apply this hotfix only to systems that are experiencing this specific problem.

If the hotfix is available for download, there is a "Hotfix download available" section at the top of this Knowledge Base article. If this section does not appear, submit a request to Microsoft Customer Service and Support to obtain the hotfix.

Note If additional issues occur or if any troubleshooting is required, you might have to create a separate service request. The usual support costs will apply to additional support questions and issues that do not qualify for this specific hotfix. For a complete list of Microsoft Customer Service and Support telephone numbers or to create a separate service request, visit the following Microsoft Web site:

http://support.microsoft.com/contactus/?ws=support (http://support.microsoft.com/contactus/?ws=support)

Note The "Hotfix download available" form displays the languages for which the hotfix is available. If you do not see your language, it is because a hotfix is not available for that language. Component:

The English version of this fix has the file attributes (or later) that are listed in the following table. The dates and times for these files are listed in coordinated universal time (UTC). When you view the file information, it is converted to local time. To find the difference between UTC and local time, use the Time Zone tab in the Date and Time tool in Control Panel.

   Date         Time   Version           Size     File name
   -----------------------------------------------------------
   05-Feb-2003  18:49  6.0.6413.0        577,536  Dsaccess.dll
   05-Feb-2003  17:58  6.0.6413.0        184,320  Dscmsg.dll
   01-Aug-2002  06:37  6.0.6300.1         84,480  Spuninst.exe

After you install this hotfix, the following event is logged in the Event Viewer Application log if this issue exists on your server:

Event ID:2112
Event Type: Warning
Event Source: MSExchangeDSAccess
Description: An attribute on objectname is too large to be cached. Requested size was size, maximum cacheable is max_size. Performance may be degraded. For more information, click http://search.support.microsoft.com/search/?adv=1.

This event is only logged if DsAccess logging has been configured to maximum. To configure DsAccess logging:

Click Start, point to Programs, point to Microsoft Exchange, and then click System Manager.
Expand your organization name, expand Administrative Groups, expand your administrative group, and then expand Servers.
Right-click your Exchange 2000 Server computer, and then click Properties.
Click Diagnostics Logging.
In the left pane, click MSExchangeDSAccess Service, and then click Cache in the right pane.
Under Logging Level, click Maximum, and then click OK.

Notes

After you apply this hotfix, the build logs a DsAccess warning with MsExchangeDsacess\Cache turned to maximum. You may still experience the problem that is described in this article until you decrease the size of the attribute. This fix does not modify the behavior of the Exchange DsAccess component.
It has been reported that even in the absence of the 2112 event, large ACLs may be the cause of the issue. Microsoft Product Support Services has a tool that is named ACLSize that can be used to quickly determine if this is your issue.
Because of file dependencies, this update requires Microsoft Exchange 2000 Server Service Pack 3 (SP3).

For more information, click the following article number to view the article in the Microsoft Knowledge Base:

301378 (http://support.microsoft.com/kb/301378/ ) How to obtain the latest Exchange 2000 Server service pack

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STATUS

Microsoft has confirmed that this is a problem in the Microsoft products that are listed at the beginning of this article.

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MORE INFORMATION

When this issue occurs, Exchange servers may start losing connectivity to domain controllers. And, the Exchange servers may receive incorrect topology information from DSAccess. The following events may be logged in the event log:

Event Type: Information
Event Source: MSExchangeDSAccess
Event Category: Topology
Event ID : 2080
Computer: SERVERNAME
Description: Process EMSMTA.EXE (PID=4232). DSAccess has discovered the following servers with the following characteristics: (Server name | Roles | Reachability | Synchronized | GC capable | PDC | SACL right | Critical Data | Netlogon | OS Version) In-site: DC-Server003.DOMAIN_NAME.COM CDG 7 7 1 0 1 1 7 1 DC-Server002.DOMAIN_NAME.COM --G 1 7 1 0 1 1 7 1 DC-Server001.DOMAIN_NAME.COM --- 0 0 0 0 0 0 0 0 DC-Server001.DOMAIN_NAME.COM --- 0 0 0 0 0 0 0 0 DC-Server003.DOMAIN_NAME.COM --G 1 7 1 0 1 1 7 1 DC-Server004.DOMAIN_NAME.COM --G 1 7 1 0 1 1 7 1 DC-Server006.DOMAIN_NAME.COM --G 1 7 1 0 1 1 7 1 DC-Server007.DOMAIN_NAME.COM --G 1 7 1 0 1 1 7 1 DC-Server004.DOMAIN_NAME.COM --G 1 7 1 0 1 1 7 1 DC-Server008.DOMAIN_NAME.COM --G 1 7 1 0 1 1 7 1
Out-of-site:
Child-DC-Server002.child.DOMAIN_NAME.COM --- 0 0 0 0 0 0 0 0 Child-DC-Server001.child.DOMAIN_NAME.COM --G 1 7 1 0 1 1 7 1 Child-DC-Server005.child.DOMAIN_NAME.COM --G 1 7 1 0 1 1 7 1 Child-DC-Server003.child.DOMAIN_NAME.COM --G 1 7 1 0 1 1 7 1

Event ID: 2070
Category: Topology
Source: MSExchangeDSAccess
Type: Information
Machine: SERVERNAME
Message: Process EMSMTA.EXE (PID=3888). DSAccess lost contact with domain controller DCNAME.DOMAIN.COM. Error was 80040933 (000021A8: LdapErr: DSID-0C060529, comment: The server is sending data faster than the client has been receiving. Subsequent requests will fail until the client catches up, data 0, vece). DSAccess will attempt to reconnect with this domain controller when it is reachable.

These symptoms may appear to be network connectivity issues. However, these symptoms may occur if the ACL sizes exceed 32 KB. Sometimes, the domain controllers and the network may not appear to be overused.

To work around this issue, reduce the ACL sizes on the Exchange Configuration objects.

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