Virtual Memory

Virtual Memory
Another thing you may need to configure is virtual memory. Virtual memory uses what’s called a
swap file, or paging file. A swap file is actually hard-drive space into which idle pieces of programs
are placed, while other active parts of programs are kept in or swapped into main memory. The
programs running in Windows believe that their information is still in RAM, but Windows has
moved the data into near-line storage on the hard drive. When the application needs the information
again, it is swapped back into RAM so that it can be used by the processor.
Because the concept of virtual memory can sometimes be hard to grasp, here is an analogy.
When you are working in your office and need a document, you may have to walk to a file cabinet
to get it. You then return to your seat and read the document. When you have finished and
are ready to go on to another task, you need to put down the current document. If you don’t
need it again in the near future, you should get up and put it back in the file cabinet. However,
if you will need it again, you may just set it on your desk for easier access. When you need the
document again, you have to pick it back up (unless you can remember what it said without
looking again). Generally, you can think of a computer’s disk drive as the file cabinet and virtual
memory as the desk.
Random access memory (RAM) is the computer’s physical memory. The more RAM you
put into the machine, the more items it can remember without looking anything up. And the
larger the swap file, the fewer times the machine has to do intensive drive searches. The maximum
possible size of your swap file depends on the amount of disk space you have available
on the drive where the swap file is placed:
 Windows XP configures the minimum and maximum swap file size automatically, but if
you want Windows to handle the size of the swap file dynamically, you have to change the
default setting by selecting System Managed Size in the Virtual Memory dialog box. We’ll
show you how to get there in a moment.
 In Windows 2000, Windows sets the minimum and maximum swap file size for you, and
you can adjust these settings. Windows 2000 handles the swap file much the same as
Windows XP. In Windows 2000 if you set a minimum and maximum size and the OS
dynamically manages the swap file size within those parameters. 2000 automatically creates
a virtual-memory swap file during installation that is approximately 1.5 times the size
of installed RAM.
In Windows 2000 and XP, the swap file is called PAGEFILE.SYS, and it’s located in the root
directory of the drive on which you installed the OS files. The swap file is a hidden file, so to
see the file in Windows Explorer you must have the folder options configured to show hidden
files. Typically, there’s no reason to view the swap file in the file system, because you’ll use
Control Panel to configure it. However, you may want to check its size, and in that case you’d
use Windows Explorer.

To modify the default Virtual Memory settings, follow these steps:
 In Windows 2000, click Start  Settings  Control Panel. Double-click the System icon
and select the Advanced tab. Then click Performance Options and, in the Virtual Memory
area, click Change.
 In Windows XP, click Start  Control Panel. Double-click the System icon, and select the
Advanced tab. In the Performance area, click Settings. Next, click the Advanced tab (yes,
another Advanced tab), and then, in the Virtual Memory area, click Change.
Note that in addition to changing the swap file’s size and how Windows handles it, you can
also specify the drive on which you want to place the file.