Microsoft KB Archive/940173

= Error message when you use the Distributed COM Configuration Properties tool (Dcomcnfg.exe) in a cluster environment: &quot;MSDTC on server is unavailable&quot; =

Article ID: 940173

Article Last Modified on 8/7/2007

-

APPLIES TO


 * Microsoft COM+ 2.0 Standard Edition

-



SYMPTOMS
When you use the Microsoft Distributed COM Configuration Properties tool (Dcomcnfg.exe) in a cluster environment, you may receive an error message that resembles the following:

MSDTC on server  is unavailable.



CAUSE
This issue may occur if an insufficient number of ports are available in the remote procedure call (RPC) dynamic port allocation range that is used by Microsoft Distributed Transaction Coordinator (MS DTC). Each instance of the Distributed COM Configuration Properties tool may use more than 70 User Datagram Protocol (UDP) ports. Therefore, multiple instances of the Distributed COM Configuration Properties tool may result in an insufficient number of ports that are available.



WORKAROUND
To work around this issue, use one of the following methods.

Method 1: Use one instance of the Distributed COM Configuration Properties tool
To configure Microsoft COM+ applications, use one instance of the Distributed COM Configuration Properties tool.

Method 2: Increase the number of ports that are available
Increase the number of ports in the RPC dynamic port allocation range.



MORE INFORMATION
The Distributed COM Configuration Properties tool uses RPC over UDP to communicate with the cluster. When the Distributed COM Configuration Properties tool uses RPC over UDP, the ports may not be released for reuse immediately. The ports are not released to prevent messages from being retransmitted or to prevent stale messages from colliding with current messages. Therefore, the Distributed COM Configuration Properties tool may use many ports.

Windows Vista uses RPC over TCP. Therefore, this problem does not occur in Windows Vista.

Keywords: kbdcom kbtshoot kberrmsg kbprb KB940173

-

[mailto:TECHNET@MICROSOFT.COM Send feedback to Microsoft]

© Microsoft Corporation. All rights reserved.