What is... Virtual Memory

Understanding why you get those "Virtual Memory" messages

Author:  Paul Landers

RAM (Random Access Memory or memory) comes in two forms - real and virtual. "Real" RAM comes in the form of memory modules (also referred to as memory cards, memory chips or memory sticks). You can read a more detailed article about RAM here. Virtual Memory is a space reserved on your Hard Disk Drive to act as a memory overflow It's far more technical than that, but we aren't going to get into the technicalities here). When the Operating System is first installed, it reserves a space on the Hard Disk Drive called a "Page File". The space it reserves is generally between 1.5 and 3 times the capacity of installed RAM in the computer.

When programs and files are opened, they are copied from the Hard Disk Drive and worked-upon in RAM. When they're "Saved" they're copied back to the Hard Disk Drive. When they're "Closed" they are removed from RAM. RAM provides the "desk space" for them to be spread-out and actioned. These open programs and files often get too large to reside in the available RAM. When this happens, the Operating System and hardware manage the overflow by placing parts of the programs and/or files in Virtual Memory (the Page File reserved on the Hard Disk Drive). Those parts are then "swapped" to and from Virtual Memory as and when they are needed.

Information in RAM can be accessed far quicker than information on a Hard Disk Drive. As such, each time information is swapped to and from Virtual Memory, the system slows down. The more that Virtual Memory has to be accessed, the more the system slows down. Additionally, and because it resides on the Hard Disk Drive, the storage space allocated to Virtual Memory (the Page File) becomed "Fragmented". You can read a more detailed article about Hard Disk Drives here. This fragmentation causes an even greater system-slowdown as files and space get more difficult to access. Eventually, the system generates a message warning you about its "Page File" or "Virtual Memory" - the exact message will vary depending on the circumstances.

So, now that we know what it's all about, what does one do if and when a Virtual Memory message is displayed? Well, if you only get the message on the rare occasion, here are some of the things you can do:

• Close (not minimise) any open files and/or programs that you are not currently using. Minimising something simply removes it from view, not from RAM.
• Defragment your Hard Disk Drive. This has the effect of "cleaning" your Page File, making it easier and quicker to access. You can read how to do that here.
• Increase the size of your Page File via the options in the Control Panel. Only do this if you're confident you know what you're doing.

If you get a "Virtual Memory" message regularly, it's likely your computer is screaming out for more RAM. You should consider upgrading the capacity of your RAM.

You can read a detailed article about maintaining and servicing your computer here.