Semaphore Timeout Error When UseWriteBehind Disabled for Redirector

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Article ID: 169742 - View products that this article applies to.
This article was previously published under Q169742
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When you disable write-behind caching in Windows NT by setting the following parameter to 0

and you then attempt to copy a file to a remote share, the following message appears:
Too many posts were made to a semaphore.


This error is caused by a problem in the redirector, which manipulates an operating system semaphore.


To resolve this problem, obtain the latest service pack for Windows NT 4.0 or Windows NT Server 4.0, Terminal Server Edition. For additional information, click the following article number to view the article in the Microsoft Knowledge Base:
152734 How to Obtain the Latest Windows NT 4.0 Service Pack

Windows NT 3.51

A supported hotfix is now available from Microsoft, but it is only intended to correct the problem that this article describes. Apply it only to systems that are experiencing this specific problem.

To resolve this problem, contact Microsoft Product Support Services to obtain the hotfix. For a complete list of Microsoft Product Support Services telephone numbers and information about support costs, visit the following Microsoft Web site:
Note In special cases, charges that are ordinarily incurred for support calls may be canceled if a Microsoft Support Professional determines that a specific update will resolve your problem. The usual support costs will apply to additional support questions and issues that do not qualify for the specific update in question.

The English version of this fix should have the following file attributes or later:
   Date      Time    Version      Size    File name     Platform
   05/29/97  06:20p               259,920 Rdr.sys       (x86)
   05/29/97  05:19p               470,928 Rdr.sys       (Alpha)
   05/29/97  05:18p               430,160 Rdr.sys       (MIPS)


To work around this problem, do one of the following:
  • Re-enable write behind caching by setting UseWriteBehind to 1


  • Apply the hotfix mentioned below.


Microsoft has confirmed that this is a problem in Windows NT 3.51, 4.0 and Windows NT Server 4.0, Terminal Server Edition. This problem was first corrected in Windows NT 4.0 Service Pack 4 and Windows NT Server 4.0, Terminal Server Edition Service Pack 4.


Article ID: 169742 - Last Review: October 7, 2013 - Revision: 2.4
  • Microsoft Windows NT Server 4.0, Terminal Server Edition
  • Microsoft Windows NT Workstation 3.51
  • Microsoft Windows NT Workstation 4.0 Developer Edition
  • Microsoft Windows NT Server 3.51
  • Microsoft Windows NT Server 4.0 Standard Edition
kbnosurvey kbarchive kbhotfixserver kbqfe kbbug kbfix KB169742

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