Topic Last Modified: 2010-09-07

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

MSExchange RpcClientAccess Per Server

Counter Name

RPC Active Backend Connections (% of Limit)

Sample Interval


Server Role

Ex14. Client Access

Critical Error Threshold


Rule Path

Microsoft Exchange Server/Exchange 2010/Client Access/Outlook

Rule Name

MSExchange RpcClientAccess Per Server RPC Active Backend Connections (% of Limit) - sustained for 15 minutes - Red (>98)


This event indicates that a particular threshold of connections between the Client Access Server (CAS) server and the Mailbox server has been reached on the Microsoft Exchange Server 2010 CAS server. If the available RPC connections are exhausted, you may experience one or more of the following symptoms in an Exchange organization:

  • MAPI clients such as Outlook hang, and the following notification appears on the client computers:

    Outlook is retrieving data from Microsoft Exchange Server <ServerName>

  • Devices such as Blackberry devices drop their connections to the server or experience timeout errors when sending and receiving messages. In this scenario, information that resembles the following may be logged on the Blackberry Enterprise Server (BES):

    • MAPI call failed. Error 'Network problems are preventing connection to the Microsoft Exchange Server computer.

One of the client access improvements that Microsoft Exchange Server 2010 includes is to support MAPI connections to the Client Access server role. This change required creating the Microsoft Exchange RPC Client Access service on the Client Access server.

The RPC Client Access service establishes an RPC endpoint on a Client Access server to which MAPI clients such as Microsoft Office Outlook can connect.

In earlier versions of Exchange, MAPI clients create an RPC connection to servers running the Mailbox server role.

In Exchange 2010, the Client Access servers communicate with Mailbox servers to give MAPI clients access to Exchange mailboxes. This new functionality gives Exchange 2010 the following advantages over earlier versions of Exchange:

  • It isolates the information store from direct client access.

  • It provides greater integration with the Exchange 2010 high availability strategy.

  • It provides a more reliable system in the event that an issue affects the information store.

For more information, see Understanding RPC Client Access.

To help reduce CPU usage on middletier servers, the Exchange 2010 CAS servers use an RPC connection pool. The RPC Active Backend Connections (% of Limit) counter represents the percentage of active connections in the RPC connection pool. This alert may be triggered when the number of available RPC connections is reduced for an extended period.

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.

  • Increase the number of Exchange 2010 CAS servers in the middletier NLB cluster.

  • 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.