Microsoft KB Archive/99768

= Optimizing Your Paging File (PAGEFILE.SYS) =

Article ID: 99768

Article Last Modified on 10/31/2006

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APPLIES TO


 * Microsoft Windows NT Advanced Server 3.1
 * Microsoft Windows NT Workstation 3.1

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This article was previously published under Q99768



Windows NT uses a paging file for virtual memory called PAGEFILE.SYS. This file is created during Windows NT Setup and is always located in the root directory. No matter what your system configuration is, Windows NT will create and use a paging file.

The paging file is not necessarily a single file; it can be a group of files stored in various locations, across hard disks and partitions. The files are collectively referred to as &quot;the paging file.&quot; When thinking about the size of the paging file, the sum of all the files that make up the paging file is the only value you need to keep in mind.

The following two guidelines should be met when optimizing the paging file:


 * 1) In general, you should set the size of the paging file to the same size as your system RAM plus 12 MB. There is a minimum size requirement of 22 MB for the operating system. If system RAM plus 12 MB is less than 22 MB, increase the size of the paging file until your system RAM plus paging file is at least 22 MB. NOTE: 22 MB is just what the operating system requires for itself. For reasonable application performance, a 40 MB total is recommended.

These sizes are recommended because Windows NT requires &quot;backing storage&quot; for everything it keeps in RAM. If Windows NT requires more space in RAM, it must be able to swap out code and data to either the paging file or the original executable file. If Windows NT cannot do this, out of memory errors will be generated.

If you set your paging file to system RAM plus 12 MB and you still get low memory warnings, try increasing the size of the paging file. If you need more disk space and you are not getting memory warnings or memory-related problems, you can try to decrease the size of the paging file.

Also, if you have enough surplus RAM to support the operating system and application memory requirements, the need for a large paging file is lessened. If you have, for example, 64 MB of RAM, you may be able to safely reduce your paging file to a very small size.
 * 1) If you have multiple hard disks, splitting up the paging file is a good idea, as it will speed up the access time. If you have two hard disks, and you split the paging file, both hard disks can be accessing information simultaneously, greatly increasing the throughput. However, if you have two hard disks, and one hard disk is faster than the other, it may be more effective to store the paging file on only the faster hard disk. Some experimentation may be necessary to arrive at the best configuration for your system.

Note: There is no point in splitting up the paging file between multiple partitions as it does not increase the ability of the hard disk to access the paging file. This may be a good idea, however, if your logical drives aren't large enough for the entire paging file.

Additional query words: page file

Keywords: kbother KB99768

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