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 depend 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 is a matrix of evaluations used by the Exchange Server Analyzer to determine whether this value is out-of-bounds for a given Exchange server. If the conditions in the matrix are matched, an error is displayed.

Operating system	Boot.ini setting	Current nonpaged pool is
Windows 2000 Server or Advanced Server	/3GB	110 MB or more
Windows 2000 Server or Advanced Server	None	220 MB or more
Windows Server™ 2003	/3GB	110 MB or more
Windows Server 2003	None	220 MB or more

The PoolNonpagedBytes key value is the size, in bytes, of the kernel memory nonpaged pool. The nonpaged pool is an area of physical system memory for objects that cannot be written to disk but must remain in physical memory as long as they are allocated. This value for this key is the last observed value. On a healthy Exchange server, this value should remain level. If the value for this counter is steadily increasing, it could indicate a memory leak.

Because there is no way to increase the limit for nonpaged 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 nonpaged pool memory can be accessed by the Windows operating system. If Windows runs out of kernel memory, it can display error messages and crash. Kernel memory is necessary for the correct operation of the system, and therefore you should monitor kernel memory carefully.

If after restarting the Exchange server, this condition is repeated, the next step is to ensure that your system is tuned correctly and that all 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 installed and running third-party applications
  
  

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

To correct this error

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

• 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)
  
  

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