Virtual Memory

Virtual memory is used to supplement the amount of physical memory you have on your computer. For example, if your computer doesn’t have enough physical RAM to run a program or task Windows XP or Windows Vista will use the virtual memory to compensate. The operating system takes your available RAM and combines it with temporary space set aside on your hard disk drive. When you are running low on memory, the data will be moved from RAM and onto a “paging file”. This frees up physical memory and allows you to continue your operations.

The more RAM you have, the faster your computer performs. While it’s tempting to make your virtual memory larger in order to get improved performance, it’s not always the right move. For example, your computer reads data from physical RAM much faster than it can read data from virtual memory. If your PC is slow due to lack of RAM, adding physical memory usually yields the best results.

Virtual memory errors occasionally occur. Typically, you might see a low virtual memory error. For example:

Limited Virtual Memory - Your system is running without a properly sized paging file. Use the virtual memory option of the System applet in the Control Panel to create a paging file, or to increase the initial size of your paging file.

To overcome this, you can create a new paging file (if yours is missing) or manually adjust the size of your virtual memory if you find the default size isn’t enough.

Windows automatically sets the minimum paging file size to the total amount of your RAM plus 300 MB. In addition, the default maximum size that Windows will allow is three times the amount of RAM. If you are encountering low virtual memory errors at these defaults, you’ll want to tweak these settings.

Go to the Start button, choose Control Panel, click either the Advanced tab(XP) or the Advanced System Settings link (Vista), choose Performance, Settings, Advanced, and find Virtual Memory. Click on the Change button to make adjustments.

Windows always uses virtual memory, even when the demands on the physical memory are low. A good rule of thumb when setting the page file size is 1.5 times the amount of physical memory. For example, if you have 2 gigabytes of RAM installed on your PC, a paging file size of 3 gigabytes should be an appropriate place to start providing you have the hard drive space to accommodate this amount.

When your hard drive starts to get full, you’ll often find yourself with a variety of memory-related errors including virtual memory errors. Clear out your temporary files and defragment your hard disk to free up space on your hard drive. If your hard drive is nearing capacity, it may be time to upgrade. In the meantime, you may want to adjust the maximum paging file size downwards until you find a compromise you can live with.