Physical memory might be the vital lubricant of a happily humming Windows machine, but Windows is not designed to run on RAM chips alone, no matter how many of them you have. In addition to using physical RAM to store programs and data, Windows creates a hidden file on your primary hard disk and uses that file to swap pages of data out of physical memory when necessary. The “swap file” (these days more commonly called a page file) acts as an extension of main memory—or, in other words, as virtual memory.
In a default installation, Windows creates the page file in the root folder on the same drive that holds the Windows system files. The size of the page file is determined by the amount of RAM in your system. By default, the minimum size is 1.5 times the amount of physical RAM, and the maximum size is three times the amount of RAM (twice the minimum). You can see the page file in a Windows Explorer window if you configure Windows to show hidden and system files; look for Pagefile.sys in the root of your system drive.
To see the current configuration of your system’s virtual memory, open Control Panel, click System And Maintenance, click Performance Information And Tools, click Advanced Tools (in the Tasks pane at the left side of the dialog box), and then click Adjust The Appearance And Performance Of Windows. After answering the UAC prompt, you’ll arrive at the Performance Options dialog box. You’re nearly there; click the Advanced tab, and then click Change.
By default, Windows creates a single page file in the root folder on the same volume that holds the Windows system files and manages its size for you. The Currently Allocated number near the bottom of the dialog box shows you how large the file is now. If conditions on your system change (you run an unusually large assortment of memory intensive applications, for example), Windows might expand the page file. It might then return the file to its original size (or a smaller size) if the demand subsides. All this happens without intervention or notification if you leave the Automatically Manage Paging File Size For All Drives check box selected.
If you don’t want Windows to do this for you, you have the following options:
+ You can move the page file to a different volume, if you have more than one.
+ If you have more than one volume, you can establish more than one page file.
+ For any page file, you can choose between System Managed Size and Custom Size.
+ If you choose Custom Size, you can specify an initial size and a maximum size.
+ You can remove a paging file from a volume by selecting the volume and choosing No Paging File. (You can even get rid of all paging files this way, although doing so is not recommended, even on systems with a lot of RAM.)
Should you get involved in page-file management, and, if so, how?
If you have more than one physical disk, moving the page file to a fast drive that doesn’t contain your Windows system files is a good idea. Using multiple page files split over two or more physical disks is an even better idea, because your disk controller can process multiple requests to read or write data concurrently. Don’t make the mistake of creating two or more page files using multiple volumes on a single physical disk, however.
If you have a single hard disk that contains C, D, and E volumes, for example, and you split the page file over two or more of these, you might actually make your computer run more slowly than before. In that configuration, the heads on the physical disk have to do more work, loading pages from different portions of the same disk sequentially, rather than loading data from a single contiguous region of the hard disk.
If you are short of hard disk space, you might consider setting a smaller initial page file size. You can use a handy script from Windows MVP Bill James to monitor current page file usage and session peak usage. This tool, a free download at http://www.vista-io.com/2102, was written for Windows XP but works fine in Windows Vista. If this script nearly always shows current and peak usage levels well below the current page file size, you might want to consider reducing the initial size to save disk space. On the other hand, if you’re not short of disk space, there’s nothing to be gained from doing this and you might occasionally overload your custom settings, thereby degrading the performance of your system.
Should you enlarge your page file? Most users won’t need to do this. But you might want to keep an eye on the green line in the Memory graph of Resource Overview. If that line is spiking off the top of the graph a great deal of the time during your normal work, you might consider increasing the maximum size of your page file. (Disregard page file spikes and disk activity in general that takes place while you’re not actually working. This is likely to be the result of search indexing, defragmentation, or other background processes and does not indicate a problem with your actual work performance.)
Note:
For more information about page file management in Windows, we recommend the article “Virtual Memory in Windows XP,” at http://vista-io.com/2103 Although the file magnitudes discussed in this article are pertinent to the XP environment rather than to Windows Vista, the basic information about how Windows manages and uses page files is still useful and valid.
