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Nonpaged Pool is over the error threshold

[This topic is intended to address a specific issue called out by the Exchange Server Analyzer Tool. You should apply it only to systems that have had the Exchange Server Analyzer Tool run against them and are experiencing that specific issue. The Exchange Server Analyzer Tool, available as a free download, remotely collects configuration data from each server in the topology and automatically analyzes the data. The resulting report details important configuration issues, potential problems, and nondefault product settings. By following these recommendations, you can achieve better performance, scalability, reliability, and uptime. For more information about the tool or to download the latest versions, see "Microsoft Exchange Analyzers" at http://go.microsoft.com/fwlink/?linkid=34707.]  

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


110 MB or more

Windows 2000 Server or Advanced Server


220 MB or more

Windows Server™ 2003


110 MB or more

Windows Server 2003


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.

  1. Restart the Exchange Server computer at the earliest convenience.

  2. Monitor the Memory | Pool Nonpaged Bytes performance counter to ensure that it is not climbing over the above listed threshold for your system.

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

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