Possible categorizer overload

[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 includes a performance data collection engine that is used to query performance counter objects on computers that are running Exchange 2000 Server or Exchange Server 2003. The performance data collection engine collects data from the Cat: Messages submitted/sec and the Cat: Categorizations completed/sec performance counters of the SMTP Server performance object to analyze performance data.

The Cat: Messages submitted/sec performance counter shows the number of messages submitted per second to the categorizer whereas the Cat: Categorizations completed/sec shows the rate of categorizations completed per second.

The Exchange Server Analyzer compares the average total of the two counters to determine whether more messages are consistently submitted than are processed.

If the Exchange Server Analyzer determines that the average total number of messages submitted per second to the categorizer is consistently greater, by two messages, than the average total number of messages completed per second, the Exchange Server Analyzer displays a warning.

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.

This warning indicates that the categorizer may be under stress. Possible causes should be investigated and remedied where you can.

Categorizer stress can be caused 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 these Microsoft TechNet Articles.

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