Topic Last Modified: 2005-11-18

The Microsoft® Exchange Server Analyzer Tool queries the Win32_PerfRawData_PerfOS_Memory Microsoft Windows® Management Instrumentation (WMI) class to determine the current value for the PoolNonpagedBytes key. The actions taken by the Exchange Server Analyzer depends on the underlying operating system, the presence or absence of the /3GB switch in the Windows Boot.ini file, and the discovered value for this key.

The following table displays the matrix of evaluations used by the Exchange Server Analyzer to determine whether this value is out-of-bounds for a specified Exchange server. If the conditions in the following table are matched, a warning is displayed.

Operating System	Boot.ini Setting	Current Non-Paged Pool is
Microsoft Windows 2000 Server or Advanced Server	/3GB	100 MB or more
Microsoft Windows 2000 Server or Advanced Server	None	200 MB or more
Microsoft Windows Server™ 2003	/3GB	100 MB or more
Microsoft Windows Server 2003	None	200 MB or more

The PoolNonpagedBytes key value is the size, in bytes, of the kernel memory non-paged pool. This is an area of physical system memory for objects that cannot be written to disk even when they are not being used. This value for this key is the last observed value. On a healthy Exchange server, unless a backup or restore is occurring, there should be no more than 85 MB of non-paged pool memory being used.

In Windows 2000 Server and Windows 2000 Advanced Server, the maximum value for non-paged pool memory is 256 MB. Because you cannot increase the limit for non-paged pool memory beyond the values listed above, this condition should be corrected as soon as possible. Regardless of the operating system in use or the presence or absence of the /3GB switch, only so much non-paged pool memory can be accessed by Windows. If Windows runs out of kernel memory, it can display error messages and crash. Kernel memory is essential to the correct operation of the system, and therefore you should monitor kernel memory carefully.

If after restarting the Exchange Server this condition recurs, the next step is to ensure that your system is tuned correctly and that all of the software and hardware on this system is up to date. This includes installing the latest:

• Windows operating system service pack
  
  
• Exchange Server service pack
  
  
• Hardware firmware and drivers
  
  
• System BIOS updates
  
  
• Updates for any third-party applications that are installed and running
  
  

If software and hardware updates do not resolve this problem, you should disable all third-party software, restart the Exchange Server computer, and monitor kernel memory.

To correct this error

For more information about tuning Exchange Server correctly, see the following Microsoft Knowledge Base articles and white papers:

• 815372, "How to Optimize Memory Usage in Exchange Server 2003" (http://go.microsoft.com/fwlink/?linkid=3052&kbid=815372)
  
  
• 266096, "XGEN: Exchange 2000 Requires /3GB Switch with More Than 1 Gigabyte of Physical RAM" (http://go.microsoft.com/fwlink/?linkid=3052&kbid=266096)
  
  
• "Troubleshooting Exchange Server 2003 Performance" (http://go.microsoft.com/fwlink/?LinkId=47588)
  
  
• "Troubleshooting Exchange 2000 Server Performance" (http://go.microsoft.com/fwlink/?LinkId=18177)
  
  
• "Exchange Server 2003 Performance and Scalability Guide" (http://go.microsoft.com/fwlink/?LinkId=47576)
  
  

For more information about the nonpaged pool memory and related topics, see the following Knowledge Base articles:

• 294418, "Comparison of 32-Bit and 64-Bit Architecture" (http://go.microsoft.com/fwlink/?linkid=3052&kbid=294418)
  
  
• 177415, "How to Use Memory Pool Monitor (Poolmon.exe) to Troubleshoot Kernel Mode Memory Leaks" (http://go.microsoft.com/fwlink/?linkid=3052&kbid=177415)
  
  
• 268343, "Umdhtools.exe: How to Use Umdh.exe to Find Memory Leaks" (http://go.microsoft.com/fwlink/?linkid=3052&kbid=268343)
  
  

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