 - Virtual (or logical) memory is a feature in an operating system that improves a computer's performance by using hard drive space to extend the storage space that's available to random access memory (RAM). One of the jobs an operating system has is to make sure that RAM, which is a finite resource, is not wasted.
When available RAM becomes fragmented into small, scattered pieces that are too small to be used by applications, it's the responsibility of the operating system (OS) to move all the little pieces of memory together into a block that can be used. If there is code and data in RAM that the processor doesn't need immediately, the operating system has the power to move that code and data to the hard drive.
Basically, the OS swaps out what can be spared from RAM so that new files the processor needs can be swapped in. Swap files, which are called page files in the Windows operating system, are stored temporarily on the larger, but slower, hard drive. The size limit for a page file is determined by how much RAM the computer has. In Windows XP, for instance, the default for page files is 1.5 times the amount of RAM.
The operating system keeps track of where it has moved things with a memory manager. The memory manager maintains a record of addresses so when the processor or an application is looking for something the operating system has moved, the operating system can find it and move it back. All this happens very quickly. When things are working right, neither the processor nor the application nor the end user knows that anything was ever moved.
Sometimes, however, the memory manager spends too much time moving things back and forth and the computer's response time slows down. If this happens, the end user can do one of several things to assist the memory manager and improve efficiency:
- Close any applications that have been left open but are not being used.
- Adjust the size of the page files.
- Purchase and install more RAM.
Learn more
Ronald Hudkins explains how to adjust the size of page files in "How to Eliminate the Virtual Memory Error Message in Windows."
Learn how to create multiple page files to optimize Windows 2000's Virtual Memory Manager.
| LAST UPDATED: |
08 May 2009
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