DOCUMENT:Q78303  24-Sep-1996  [winnt]
TITLE   :Windows NT File Corruption Problem 
PRODUCT :Microsoft Windows NT 
PROD/VER:  4.00
OPER/SYS:WINDOWS
KEYWORDS:kbnetwork kbbug4.0

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The information in this article applies to:

 - Microsoft Windows NT Workstation version 4.0
 - Microsoft Windows NT Server version 4.0

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SYMPTOMS
========

If files are rapidly accessed on a Windows NT File server, intermittent data corruption may occur.   Microsoft Internet News Server data files may exhibit these symptoms.   The problem is more likely to be observed on a Multiprocessor system.

CAUSE
=====

If an application is performing a write-extend of a file, the cache manager read ahead thread is also reading the current last page of the file as part of a larger read.  The read ahead thread issues the read and the write is blocked waiting for the read to complete.   Due to a timing problem that may occur, the memory manager wakes the write thread associated with the IO operation.  This thread will place null characters in the last page which is beyond the current file size and then write the new data into the page.  The read thread wakes up and also zeroes the last page after the write thread has written the new data.  The update to the page is lost and null characters are appended in the file instead of the data which should have been committed for the IO operation.

RESOLUTION
==========

Obtain the fix mentioned below or wait for the next Windows NT service pack.

STATUS
======

Microsoft has confirmed this to be a problem in Windows NT version 4.0. A 
supported fix is now available, but has not been fully regression-tested 
and should be applied only to systems experiencing this specific problem. 
Unless you are severely impacted by this specific problem, Microsoft 
recommends that you wait for the next Service Pack that contains this fix.
Contact Microsoft Product Support Services for more information.

This hotfix has been posted to the following Internet location:

 ftp://ftp.microsoft.com/bussys/winnt/winnt-public/fixes/usa/NT40/hotfixes-preSP1/krnl-fix

KBCategory: kbnetwork kbbug4.0
KBSubcategory: ntnetserv
Additional reference words: prodnt 4.00 

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