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Q163880: COPY Command Causes File Cache to Grow

Article: Q163880
Product(s): Microsoft Windows NT
Version(s): winnt:4.0
Operating System(s): 
Keyword(s): kbnetwork
Last Modified: 08-AUG-2001

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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
========

When you use the COPY command of Cmd.exe to copy files that are significantly
larger than the physical memory, Windows NT appears to slow down and user
interface performance decreases.

When you look at this in performance monitor, the cache is very large (from 50 to
90 percent of physical memory) and the process working sets have shrunk.

MORE INFORMATION
================

The CreateFile API has a flag (FILE_FLAG_SEQUENTIAL_SCAN) that is useful when
copying files. It tells Cache Manager to not grow the file cache when requests
for this handle arrive. Therefore, Memory Manager does not have to shrink the
application's working set to accommodate the larger cache. The CopyFile and
CopyFileEx APIs make use of this flag.

Although the COPY command uses the CopyFile API, it opens the file without the
mentioned flag first to inspect the source and destination files.

WORKAROUND
==========

Use XCOPY, File Manager or Windows Explorer to copy large files.

RESOLUTION
==========

To resolve this problem, obtain the hotfix mentioned below.

STATUS
======

Microsoft has confirmed this to be a problem in Windows NT version 4.0. This
problem was corrected in the latest Microsoft Windows NT 4.0 U.S. Service Pack.
For information on obtaining the service pack, query on the following word in
the Microsoft Knowledge Base (without the spaces):

  S E R V P A C K


Additional query words:

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Keywords          : kbnetwork 
Technology        : kbWinNTsearch kbWinNTWsearch kbWinNTW400 kbWinNTW400search kbWinNT400search kbWinNTSsearch kbWinNTS400search kbWinNTS400
Version           : winnt:4.0
Issue type        : kbbug

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