Topic Last Modified: 2010-07-06

The Microsoft Exchange Server 2010 Management Pack for System Center Operations Manager includes a performance data collection engine that is used to query performance counter objects on computers running Exchange 2010. For this Operations Manager rule, data is collected by using the performance counter specified in the Details table.

To review the value of the performance counter that generated this alert, in Operations Manager, double-click this alert, and then click the General tab. Review the description of the alert that includes the variables specific to your environment.


Product Name


Product Version

14.0 (Exchange 2010)

Object Name


Counter Name

% Processor Time

Instance Name


Sample Interval


Server Role

Ex14. Mailbox

Critical Error Threshold


Rule Path

Microsoft Exchange Server/Exchange 2010/Mailbox/Assistants

Rule Name

MSExchangeAssistants CPU


This event indicates that a high percentage of processor time is being used by Mailbox Assistants. A high value may indicate that a processor bottleneck exists. For more information, see Examining the Processor Time Counter.

In this scenario, the Microsoft Exchange Server 2010 mailbox server may be slow to respond to user requests. When this occurs, all activities that are performed by Mailbox Assistants may take longer to process or may experience intermittent failures.

The Assistant Infrastructure is part of the hosting application installation on servers that host the Mailbox server role. The Assistant Infrastructure is the component in Exchange 2010 that separates message processing business logic from the information store. The separation of business logic from the store has the advantage of reducing the load on the store. This makes it easier to implement changes in business logic design and testing. Some of this business logic includes the following features:

  • E-mail retention

  • Resource scheduling

  • Automated out-of-office messages

  • Automated calendaring features

To handle business logic processing, the Assistant Infrastructure uses event-based and assistants and time-based assistants known as Mailbox Assistants. Event-based assistants process tasks that are based on events from the information store. Time-based assistants process tasks that are based on schedules. If insufficient CPU time is available, the assistants may take a long time to update mailbox information.

User Action

To resolve this problem, do one or more of the following:

  • Review the Application log and System log on your Exchange 2010 servers for related events. For example, events that occur immediately before and after this event may provide more information about the root cause of this error.

  • To review detailed information about the cause of this problem, use the Operations Console in Operations Manager. For more information, see the "Introduction" section in this topic.

  • Examine the event log entries for each Assistant Infrastructure and for each corresponding Assistant to determine whether any exceptions. You may have to increase diagnostics logging to generate additional events. Any event that is generated in the Application log will include the exception type. You can use the information to help determine the cause of the excessive CPU usage.

  • Collect performance information for all the Assistant Infrastructure counters by using the MSExchange Assistants object. Also, collect performance data for each Assistant object.There is one instance for every hosting application per database on the server. The instance name contains the service name of the hosting application's service together with the database name. Also, there is a total instance for every hosting application. The "total" captures consolidated values for every counter for all assistants that are hosted by the application.

  • Examine the Client Access servers in the middletier NLB cluster to verify that all the servers are available.

  • Verify that DNS entries are configured correctly to perform appropriate round-robin processing of Client Access Server (CAS) servers.

  • If the CAS servers in the middletier are overloaded, add CAS servers to the network load balancing array, as required.

  • Resolve your issue by using self-support options, assisted support options, and other resources. You can access these resources from the Exchange Server Solutions Center. From this page, click Self-Support Options in the navigation pane to use self-help options. Self-help options include searching the Microsoft Knowledge Base, posting a question at the Exchange Server forums, and others. Alternatively, in the navigation pane, you can click Assisted Support Options to contact a Microsoft support professional. Because your organization may have a specific procedure for directly contacting Microsoft Technical Support, be sure to review your organization's guidelines first.

For More Information

If you are not already doing so, consider running the Exchange tools created to help you analyze and troubleshoot your Exchange environment. These tools can help make sure that your configuration aligns with Microsoft best practices. They can also help you identify and resolve performance issues, improve mail flow, and better manage disaster recovery scenarios. To run these tools, go to the Toolbox node of the Exchange Management Console. To learn more about these tools, see Managing Tools in the Toolbox.