Microsoft KB Archive/115522

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Limits on Overlapped Pipe Operations

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Q115522

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The information in this article applies to:


 * Microsoft Win32 Application Programming Interface (API), included with:
 * the operating system: Microsoft Windows NT, versions 3.1, 3.5, 4.0
 * the operating system: Microsoft Windows 2000

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SUMMARY
The Windows NT version 3.1 redirector allows only 17 outstanding overlapped pipe operations at any given time. The Windows NT 3.5 redirector does not have this restriction on overlapped pipe writes. However, the Windows NT 3.5 redirector allows only 17 outstanding overlapped pipe reads at any given time.

If the client uses overlapped I/O through the redirector, it is possible for the client to become deadlocked. You may need to increase the number of threads that the redirector uses for I/O; the same thing is true for the server. If your application is doing a lot of I/O, you can avoid this deadlock by creating extra threads and having them use non-overlapped I/O.

MORE INFORMATION
Increasing the workstation services MaxThreads parameter increases the number of kernel threads that the redirector will create, thus allowing more operations to be outstanding at any given time.

This parameter is located in:

  HKEY_LOCAL_MACHINE\SYSTEM\ CurrentControlSet\ Services\ LanmanWorkstation\ Parameters\ MaxThreads The parameter can be set from 0 to 255 (the default is 17).

Additional query words: 3.10 3.50 maximum threads

Keywords : kbAPI kbFileIO kbOSWinNT310 kbOSWinNT350

Issue type : kbinfo

Technology : kbAudDeveloper kbWin32sSearch kbWin32API