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When you launch an application, one of the first things it does is stake a claim to as much RAM as it will need to run. Windows does its best to save room in system memory for all the applications you want to run, but sooner or later, it will hit the wall.
When Windows runs low on real memory, it dips into virtual memory. Virtual memory is a way of tricking applications into thinking there's more RAM in your computer than there really is, by creating a file on your hard drive called a swap file. When an application needs more memory, Windows makes more available by searching for old or inactive application data in its RAM and moving it to the swap file. Accessing a hard drive is slower than accessing RAM, so if an application later needs some of the data that Windows moved to the swap file, the OS (operating system) moves it back to RAM. To make room for this data, Windows again looks for inactive data to move to the swap file. This searching and swapping takes time; depending on how often it occurs, it can also take a performance toll.
Take Control Of Your Swap File
Virtual memory settings let you specify who controls the swap file, you or Windows. The default is Windows, but in most cases you can probably do a better job. You can set minimum and maximum size limits for your swap file, as well as its location, and if you want you can even disable virtual memory altogether.
If your swap file is small or fragmented or you have limited RAM, your system may spend most of its time moving data to and from the swap file, a process known as thrashing. Proper swap file management is the key to limiting thrashing and getting better performance from your computer's memory.
When Windows needs more swap space, it enlarges the swap file, taking over all available drive space if necessary. When demand levels off, Windows decreases the size of the swap file again. This dynamic sizing of the swap file causes a great deal of confusion about how to manage it.
Dynamic swap file sizing began with Windows 95, but because of poor implementation the feature frequently caused performance hits. As such, if you use Win95, you're usually better off specifying a fixed size for your swap file. Windows 98 and Windows Me do a better job, and most users can now comfortably let Windows manage the size of their swap files. But there's still a benefit to taking control, as specifying a minimum swap file size can prevent fragmentation of the file area Windows uses most often for swapping.
Determine optimal swap file size. Many people have favorite formulas for determining swap file size; some claim it should be three times the amount of RAM your PC has, and others prefer multiplying system memory by 1.5. Either way, RAM-based sizing formulas are flawed for one important reason: The less RAM you have, the more swap file space you will need. Likewise, the more RAM you have, the less swap space you'll need.
It's better to set swap file size based on your usage than on a formula that is more urban legend than reality. To determine how large your swap file should be, run the System Monitor utility. (This utility is an optional component of Win95, Win98, and WinMe. If it's not currently installed, you can install it from your Windows CD.)
To launch System Monitor, click the Start button, point to Programs, Accessories, and System Tools, then click System Monitor. Click the Edit menu, then Add Item. Select Memory Manager from the Category: field, then click Swapfile Size in the Item: field and click OK. Minimize the System Monitor window and resume using your computer. Before you shut down your PC at the end of the day, maximize System Monitor and check the Memory Manager: Swapfile Size chart. Click the graph, and System Monitor will display the peak value (largest swap file size) at the bottom of the window. Run System Monitor for several days to get a better feel for your overall usage.
If you use Win98 or WinMe, use the peak value as the minimum setting for your swap file size. If you use Win95, add 20% and use that value as both your minimum and maximum settings.
Let System Monitor run in the background while you spend a typical day working on your computer. At the end of the day, check the peak value of the swap file on the Swapfile Size chart.
Location, location, location. The default location for the swap file is C:\WINDOWS\Win386.swp. If you have more than one hard drive or drive partition, you can tell Windows where to store the swap file. The default location is adequate but has some important limitations that can adversely affect performance. The swap file grows and shrinks in small steps, and when Windows needs to increase its size, it looks for the next available section of hard drive space. Because the swap file is on your C: drive, it competes for space with programs and data files, so it's not likely to find contiguous (adjacent) space for expansion. Instead, it must use the next available area on the C drive, regardless of its distance from the main swap file. As the swap file shrinks, it gives up drive real estate for use by other files. The next time the swap file needs to grow, it may need to search even farther for available space, making it even more fragmented.
To fix this problem, move the swap file to a dedicated drive or partition. A dedicated partition lets the swap file expand and shrink without the fragmentation, because it doesn't have to share space with other applications and files. A 256MB partition should be large enough to accommodate most swap files.
If you have more than one hard drive, it's best to create the swap file partition on the fastest one, preferably at the beginning of the drive.
If you only have one hard drive, Windows uses the first partition for the files it needs to boot your system. The next best location is the middle of the drive, as this area provides access times in line with your hard drive's average speed.
The least desirable location is the end of the hard drive, which has the longest read and write times, as well as potentially the longest trip for moving drive heads when accessing data.
If you create three partitions for a 10GB hard drive, for example, you might set aside 4.75GB for the first partition, which will store your OS. The second partition should consist of 256MB just for your swap file, leaving another 4.75GB for a third partition to store application files and your data.
Changing Virtual Memory Settings
Click Start, Settings, and Control Panel. Double-click the System icon, then select the Performance tab. Click Virtual Memory, and then click the radio button next to Let Me Specify My Own Virtual Memory Settings.
Win95. Enter the value you obtained from the Swap file size section, above, for both the minimum and maximum settings to prevent Win95 from creating a dynamic swap file.
Win98/WinMe. Enter the minimum size you determined from the Swap file size section, above. Leave the maximum setting as is (no maximum). This lets the swap file grow as needed but never fall below a minimum, guaranteeing that at least your main swap file will remain unfragmented.
Win95/98/Me. Choose a location for the swap file from the Hard Disk: drop-down list.
Once you make your selections, click OK. Windows will warn you that taking control of virtual memory may prevent your system from booting, or at least from working properly. Ignore these dire warnings, and click the Yes button. Restart your computer to put your changes into effect.
Disable Virtual Memory
Turning off virtual memory allows a small increase in performance, as Windows no longer has to manage the swap file or take time to move data in and out of virtual memory. On the other hand, it may also cause you to run out of system resources faster. Power users looking to eke out the last drop of performance may want to try this, although it's power users who will most likely suffer since they are the ones who usually run multiple resource-intensive applications. If you have more than 256MB of RAM, you can lower the swap file size (or perhaps even eliminate it) if you're careful about the number and types of applications you run.
Taking control of virtual memory can make your system run more efficiently. After making a change to your system, pay careful attention to its performance. By becoming more familiar with your system, you can tune it to match your particular needs and usage
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