What is Virtual Memory? (Setting the Page File size)

 By Lee Brannon

 Revised - re-posted 1/31/09

Working with computers professionally is a challenge.  The challenge is not in the technology, but in the service you provide to clients.  We sometimes forget that not everyone knows what we know. With that in mind I decided to drop in this page on the subject of Virtual Memory. I was recently asked “What is Virtual Memory”?

Have you ever noticed your computer accessing the hard drive often as you work inside an application.?  More than likely it is because your computer is out of RAM space and is now using virtual Memory.

What is virtual memory? The short answer is that it is hard disk space that the computer uses for swapping in and out seldom accessed data or for “extra” memory when the physical RAM in your computer becomes full. Unfortunately it is one of those terms that Microsoft decided to “change”. Windows XP and Vista references all use the term “paging” or page file space or paging file sizes etc.

Basically the virtual Memory is written and read in “Pages” of memory or disk space. The size can be adjusted to make the machine faster or slower. Adjusting up or down is not a straight forward process. Either way can slow down the machine.

I of course do not know what Operating System you are running but it will be relatively the same process in all of them. In Windows XP you can set how large the “page file” size is through the System properties.

Right click on My Computer and pick properties.

Now click the advanced TAB

Now click the Settings button under performance.

Now click the “other” advanced TAB.

Now click the Change button. (Notice all the page and paging references?)

It is generally best if you select the System Managed size option. (Don’t copy my settings. Every computer is different.) I recommend that you do not use the "no paging file" option.  This is generally a bad idea since If you are brave and want to see if you can speed things up with your computer you can change the settings under custom.  Keep in mind that setting it to small or to large can have adverse effects. If you are going to change the Page File size do so in small increments and test the results.  If your computer slows down make changes in the other direction.

Remember, if you get things fouled up you can always select the  "System Managed size" option again and then start over. 

Microsoft product screen shot(s) reprinted with permission from Microsoft Corporation.span>