How Windows NT 3.51 Handles Compression of Paging Files

 Last reviewed: November 9, 1995
Article ID: Q138629
The information in this article applies to:
  • Microsoft Windows NT Workstation version 3.51
  • Microsoft Windows NT Server version 3.51

SUMMARY

Windows NT provides virtual memory by creating a paging file (PAGEFILE.SYS) in the root directory of the boot drive or the root directory of the Windows NT drive (the drive where Windows NT is installed). In Windows NT 3.51, the Windows NT file system (NTFS) file system supports on-the-fly compression and decompression of files and directories. This article explains how Windows NT 3.51 handles file compression of paging files.

MORE INFORMATION

File compression in the NTFS partition is accomplished by reallocating the file during the operation. Since you cannot reallocate the paging file while it is being used, compression of an active paging file is not allowed. When you compress a file in the NTFS partition, the file is reallocated as new data is written to the file. Because reallocation of the paging file is not allowed while servicing a page fault, NTFS prevents compression on active paging files. No message appears notifying the user that this operation is not allowed.

If you have multiple installed versions of Windows NT 3.51 and multiple paging files on the same computer (each installation with its own paging file), compression of the inactive paging file is allowed. However, if you shutdown and restart another installed version of Windows NT with a compressed paging file, PAGEFILE.SYS is automatically uncompressed.

KBCategory: kbenv
KBSubcategory: ntfilesys
Additional reference words: prodnt 3.51 compact

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Last reviewed: November 9, 1995
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