DOCUMENT:Q164260 08-AUG-2001 [winnt] TITLE :Compressing and Uncompressing Files Cause File Cache to Grow PRODUCT :Microsoft Windows NT PROD/VER:winnt:4.0 OPER/SYS: KEYWORDS:kbbuglist kbfixlist ====================================================================== ------------------------------------------------------------------------------- The information in this article applies to: - Microsoft Windows NT Workstation version 4.0 - Microsoft Windows NT Server version 4.0 ------------------------------------------------------------------------------- SYMPTOMS ======== When you compress or uncompress big files, the performance of the interactive processes may suffer. This happens when the files are bigger than the physical memory of the computer. All three of the following utilities capable of compressing or uncompressing files in Windows NT show this behavior: COMPACT utility (Compact.exe) File Manager (Winfile.exe) Windows NT Explorer (Explorer.exe) When you run performance monitor during compression you will see that the cache (Memory: Cache Bytes) is very large (between 50 and 90 percent of the physical memory) and the working sets of the processes (Process: Working Set, Instance _Total) are reduced. MORE INFORMATION ================ The CreateFile API has a flag FILE_FLAG_SEQUENTIAL_SCAN that is especially useful when working on files in a sequential manner. It tells Cache Manager not to 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 bigger cache. None of the three utilities used this flag when opening the files for compression or decompression. 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: prodnt virtual memory ====================================================================== Keywords : kbbuglist kbfixlist Technology : kbWinNTsearch kbWinNTWsearch kbWinNTW400 kbWinNTW400search kbWinNT400search kbWinNTSsearch kbWinNTS400search kbWinNTS400 Version : winnt:4.0 Issue type : kbbug ============================================================================= THE INFORMATION PROVIDED IN THE MICROSOFT KNOWLEDGE BASE IS PROVIDED "AS IS" WITHOUT WARRANTY OF ANY KIND. MICROSOFT DISCLAIMS ALL WARRANTIES, EITHER EXPRESS OR IMPLIED, INCLUDING THE WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE. IN NO EVENT SHALL MICROSOFT CORPORATION OR ITS SUPPLIERS BE LIABLE FOR ANY DAMAGES WHATSOEVER INCLUDING DIRECT, INDIRECT, INCIDENTAL, CONSEQUENTIAL, LOSS OF BUSINESS PROFITS OR SPECIAL DAMAGES, EVEN IF MICROSOFT CORPORATION OR ITS SUPPLIERS HAVE BEEN ADVISED OF THE POSSIBILITY OF SUCH DAMAGES. SOME STATES DO NOT ALLOW THE EXCLUSION OR LIMITATION OF LIABILITY FOR CONSEQUENTIAL OR INCIDENTAL DAMAGES SO THE FOREGOING LIMITATION MAY NOT APPLY. Copyright Microsoft Corporation 2001.