DOCUMENT:Q235250  20-MAY-2002  [winnt]
TITLE   :I/O May Be Performed at the Wrong Offset with Large Files
PRODUCT :Microsoft Windows NT
PROD/VER:winnt:4.0
OPER/SYS:
KEYWORDS:kbWinNT4sp6fix

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The information in this article applies to:

 - Microsoft Windows NT Server version 4.0, Terminal Server Edition 
 - Microsoft Windows NT Server version 4.0 
 - Microsoft Windows NT Workstation version 4.0 
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SYMPTOMS
========

Certain file read or write operations (also known as input/output, or I/O
operations) may be performed at incorrect locations within a file that is larger
than 4 gigabytes (GB) in size.

For this problem to occur, I/O operations must be cached and asynchronous.
Unbuffered, synchronous operations are not susceptible to the problem described
in this article.

This problem can occur only when two I/O operations are performed in close
succession if the first operation is above the 4-GB mark and the second
operation is at the same offset (modulo 4 GB), below the 4-GB mark.

For example, if the first operation is performed at offset 4,295,032,832
(0x100010000 hex) and the second is performed at offset 65,536 (0x10000 hex),
the second I/O operation may actually take place at the first offset.

CAUSE
=====

In an attempt to improve performance, the cache manager attempts to perform
32-bit operations when performing certain lookup operations. 64-bit operations
are more time consuming, but are required when file offsets are large enough
that they cannot be represented in 32 bits. The problem described in this
article occurs because the cache manager occasionally errs and performs 32-bit
arithmetic when 64-bit arithmetic is required.

RESOLUTION
==========

Windows NT Server or Workstation 4.0
------------------------------------

To resolve this problem, obtain the latest service pack for Windows NT 4.0 or the
individual software update. For information on obtaining the latest service
pack, please go to:

 - http://www.microsoft.com/Windows/ServicePacks/

-or-

 - Q152734 How to Obtain the Latest Windows NT 4.0 Service Pack

For information on obtaining the individual software update, contact Microsoft
Product Support Services. For a complete list of Microsoft Product Support
Services phone numbers and information on support costs, please go to the
following address on the World Wide Web:

   http://support.microsoft.com/default.aspx?scid=fh;EN-US;CNTACTMS


Windows NT Server 4.0, Terminal Server Edition
----------------------------------------------

To resolve this problem, obtain the latest service pack for Windows NT Server
4.0, Terminal Server Edition. For additional information, please see the
following article in the Microsoft Knowledge Base:

   Q152734 How to Obtain the Latest Windows NT 4.0 Service Pack


STATUS
======

Microsoft has confirmed this to be a problem in Windows NT 4.0 and Windows NT
Server 4.0, Terminal Server Edition.

This problem was first corrected in Windows NT Server 4.0 Service Pack 6 and
Windows NT Server 4.0, Terminal Server Edition Service Pack 6.

Additional query words:

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Keywords          : kbWinNT4sp6fix 
Technology        : kbWinNTsearch kbWinNTWsearch kbWinNTW400 kbWinNTW400search kbWinNT400search kbWinNTSsearch kbWinNTS400search kbWinNTS400 kbNTTermServ400 kbNTTermServSearch
Version           : winnt:4.0
Hardware          : ALPHA x86
Issue type        : kbbug
Solution Type     : kbfix

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