Potential categorizer performance issue

[This topic is intended to address a specific issue called out by the Exchange Server Analyzer Tool. You should apply it only to systems that have had the Exchange Server Analyzer Tool run against them and are experiencing that specific issue. The Exchange Server Analyzer Tool, available as a free download, remotely collects configuration data from each server in the topology and automatically analyzes the data. The resulting report details important configuration issues, potential problems, and nondefault product settings. By following these recommendations, you can achieve better performance, scalability, reliability, and uptime. For more information about the tool or to download the latest versions, see "Microsoft Exchange Analyzers" at http://go.microsoft.com/fwlink/?linkid=34707.]  

Topic Last Modified: 2006-09-06

The Microsoft® Exchange Server Analyzer Tool queries the ExchangeLink Microsoft Windows® Management Instrumentation (WMI) class for the value of the TypePendingCategorization attribute of the Simple Mail Transfer Protocol (SMTP) ProtocolName instance to determine the number of messages in the Messages Awaiting Directory Lookup (MADL) SMTP queue.

Properties of the ExchangeLink WMI class return information about message-handling links (queues) between mail servers. A link can contain zero or more ExchangeQueue objects. This number depends on the current message traffic along the link.

The Exchange Server Analyzer also includes a performance data collection engine that is used to query performance counter objects on computers that run Exchange 2000 Server or Exchange Server 2003.

If the Exchange Server Analyzer determines that there are currently more than fifty messages in the MADL queue, the Exchange Server Analyzer has the performance data collection engine collect data from the Cat: Messages Categorized and the Cat: Categorizations completed performance counters of the SMTP Server performance object to analyze performance data.

The Cat: Messages Categorized performance counter shows the number of messages the categorizer has submitted for queuing whereas the Cat: Categorizations completed performance counter shows the total number of messages submitted to the categorizer that have been completed.

The categorizer performs the following core operations:

  • Resolves and validates all recipients.

  • Determines limits and restrictions for all recipients.

  • Expands distribution lists if that is required.

  • Determines whether the message is for local or remote delivery.

The Exchange Server Analyzer examines the average total of the two counters to determine whether their numbers increase over the sampling period.

The Exchange Server Analyzer displays an error if the following conditions are true.

  • There are fifty or more messages in the MADL queue.

  • The Cat: Messages Categorized performance counter shows an increase over the sample period that indicates progress in passing submitted messages to the next process.

  • The Cat: Categorizations completed performance counter shows an increase over the sample period that indicates progress in successfully completing the categorization of the submitted messages.

This error indicates that, although the categorizer processes messages successfully, its queue length remains high and performance may be damaged.

Categorizer performance can be affected by a demand to process many messages because of:

  • Unsolicited commercial e-mail (UCE) or spam.

  • Virus proliferation.

  • Server performance issues.

To address this warning:

  • Determine whether the stress to the categorizer is expected or from a typical load. If the stress to the categorizer is from an expected load, review the Exchange performance guidance in the following Exchange resources:

  • If the stress to the categorizer is not from an expected load, check for virus outbreaks or spam that might generate the load.


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