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Q195930: Memory Usage by MS-DOS Application Steadily Increases

Article: Q195930
Product(s): Microsoft Windows NT
Version(s): WinNT:3.51,4.0
Operating System(s): 
Keyword(s): 
Last Modified: 25-FEB-1999

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The information in this article applies to:

- Microsoft Windows NT Workstation versions 3.51, 4.0 
- Microsoft Windows NT Server versions 3.51, 4.0 
- Microsoft Windows NT Server, Enterprise Edition version 4.0 
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SYMPTOMS
========

Memory usage by any MS-DOS application that repeatedly calls the functions
_dos_findfirst or _dos_findnext may continue to grow until the application
quits. When you view the working set or private bytes using a diagnostic tool
such as Performance Monitor, the size may steadily increase over time.

CAUSE
=====

MS-DOS applications run on Windows NT under the Windows NT Virtual DOS Machine
(NTVDM) subsystem. Each time an MS-DOS application calls the _dos_findfirst API,
memory is allocated by the NTVDM and is used to keep the necessary search
context information needed to handle subsequent calls to _dos_findnext. This
memory is not deallocated until the directory search is complete or the process
ends. The amount of memory allocated for each _dos_findfirst request varies
based on the version of Windows NT, but is in the range of 1 KB to 2 KB for each
request.

RESOLUTION
==========

The only way the NTVDM can be sure a directory search has completed is when
either _dos_findfirst or _dos_findnext returns non-zero, which indicates no
matching entry. Applications should be written to finish each search, or the
application can be rewritten as a 32-bit application. Under Win32, the functions
FindFirstFile and FindNextFile replace the functions _dos_findfirst and
_dos_findnext respectively. The Win32 function FindClose is provided to
deallocate all related memory when the search handle is no longer required.

Additional query words: ntee ee console memory

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Keywords          :  
Technology        : kbWinNTsearch kbWinNTWsearch kbWinNTW400 kbWinNTW400search kbWinNT351xsearch kbWinNT400xsearch kbWinNTW351xsearch kbWinNTW351 kbWinNTSsearch kbWinNTSEntSearch kbWinNTSEnt400 kbWinNTS400xsearch kbWinNTS400 kbWinNTS351 kbWinNTS351xsearch
Version           : WinNT:3.51,4.0
Issue type        : kbprb

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