This is provided "AS IS" with no warranties, and confers no rights.

SYMPTOMS

 

Outlook clients may experience slow response times or be completely unable to connect to an Exchange Server 2003 front end server using RPC over HTPP or RPC over HTTPS.  

 

The HTTP Error logs (%SYSTEMROOT%\System32\LogFiles\HTTPERR\*.log) may contain Connections_Refused entries.

 

Kernel non-paged pool memory usage may be over 230MB.

 

 

CAUSE

 

The Microsoft Windows Server 2003 server may be running out of available non-paged pool memory. On Microsoft 32-bit operating systems, the size of the Kernel Non-Paged Pool memory is fixed, and has a maximum size of 250MB (128 MB if you have the /3GB switch in the boot.ini file). HTTP.sys is a kernel-mode driver which uses non-paged pool memory for every active RPC over HTTP connection. By design, HTTP.sys is configured to stop accepting connections when available non-paged pool memory falls below 20MB.

 

 

RESOLUTION

 

On Microsoft 64-bit operating systems, the Kernel Non-Paged pool memory limit is fixed at 128GB. This will allow HTTP.sys to handle significantly more connections.

 

If you require the ability to support large numbers of RPC over HTTP connections, then it is recommended that you move to a 64-bit version of Microsoft Windows Server 2003. Unfortunately, you cannot install Exchange Server 2003 on Windows Server 2003 (x64). Therefore, you should wait for the release of Exchange 2007 and implement an Exchange 2007 Client Access Server on Windows Server 2003 (x64).

 

WORKAROUND

 

If you require the ability to support large numbers of RPC over HTTP connections prior to the release of Exchange 2007 you can implement a Windows 2003 Server (x64) with the RPC over HTTP Proxy service enabled in place of an Exchange Server 2003 front end server. An x64 Windows 2003 server can be easily upgraded to an Exchange 2007 client access server.

 

It should be noted that there is currently no GUI to manage RPC proxy servers therefore you will need to write custom scripts to set up access via RPC over HTTP for eligible servers.

 

STATUS

 

Microsoft has confirmed that this is a 32-bit architecture limitation and affects the Microsoft products that are listed in the "Applies to" section.

 

 

 

APPLIES TO

Microsoft Exchange Server 2003 Enterprise Edition

Microsoft Exchange Server 2003 Standard Edition

 

 MORE INFORMATION

Kernel non-paged pool memory usage can be monitored by using the Memory Pool Monitor utility, Poolmon.exe, and the GFlags tool. These utilities are available in the \Support\Tools folder of the Windows Server 2003 CD.

For additional information about how to use the Memory Pool Monitor, click the following article number to view the article in the Microsoft Knowledge Base:

 

177415 (http://support.microsoft.com/kb/177415/) How to use Memory Pool Monitor (Poolmon.exe) to troubleshoot kernel mode memory leaks