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WHAT IS VIRTUAL MEMORY AND ITS ROLE

by froster_mohit - 6/16/07 1:37 PM
In reply to: What do you mean, Windows Virtual Memory is too low?! by Lee Koo (ADMIN)
Suppose you are playing a computer game and you have 128RAM installed on your computer and
your system needs 150MB of memory.What will you do?Your system may crash because of insufficient memory

Here the comes the role of virtual memory.

What is virtual memory?
Virtual memory is a part of hard disk which your operating system treat it as if it were RAM.In windows 98 and before swap files of 256 KB were used for this purpose.A major drawback was that when you close the program it does not itself deletes these swap files which in turn result loss of free disk space.Also,it was very tough for operating systems to handle these files which is result in hanging of operating system.When a program is run then only operating system can trace the size of virtual memory and create swap files.so, it result in slower performance.

But in windows 2000 and later in XP a file known as pagefile.sys was introduced which is then treated as virtual memory.By default 1.5 times the RAM is the size of virtual memory.Also being a single piece of file it is easier for an operating system to handle this file which is result in greater reliability .Also it is pre-determined so program runs quite faster in windows XP and 2000.

Now your problem is VIRTUAL MEMORY TOO LOW
This message can appear only in windows 2000 and windows XP.There may be the following reasons:-
Firstly,the size of your pagefile.sys is less than as required by the operating system
Secondly,the size of pagefile.sys is less than what recomended by your operating system that is 1.5 times the RAM
Thirdly,this message may appear if you remove pagefile.sys from drive C.(THIS IS VERY RARE)

How can you see the conditon of your virtual memory?
Right click the taskbar and choose the option windows Task manager.Click on the performance tab and here you can visualize the condition of your virtual memory.

How to configure your Virtual memory in windows XP?
Right click MY COMPUTER ICON ON your desktop and choose the option properties.A window will appear named system properties.On the Advanced tab.Click on settings tab under the heading performance.
Then a window will appear named performance options.On the Advanced tab click change underthe heading virtual memory.On the virtual memory window set the virtual memory according to your needs and according to your RAM.I will recommend you to keep virtual memory on every drive.If you are using 128MB RAM ,You should use 400MB Of virtual memory
If you have 256MB RAM,Use virtual memory upto 1GB
If you have 512MB RAM,keep the size of virtual memory to be 2.25GB

But this all not solve your problem,this message may appear if you are using above

configuration because there are still many programs which consume memory greater than this.

Ex.
For 128MB RAM users if you have adobe acrobat reader8.0 and you are opening a document of

size 100 pages and you are scrolling pages up and down many times,then this program will

need approx. 600MB of virtual memory alone.

If you have AVG anti-virus software with latest updates and you are using 512MB RAM your

memory need may rise to upto 2.5GB.
Also there are many games which alone need upto 3GB of memory.
So,you there is only one way to get rid out of problems,let the system manage its own paging file.Also you have to be aware of your system memory requirements.so,Iwill recommend you that whenever you start your operating system.Always run either task manager or process explorer(which can be downloaded from download.com)or similar program to trace the memory requirements of your system.

If you have any queries you can free in contacting me.My E-mail ID is frosterrace@yahoo.co.in
Myself Mohit from INDIA,a young boy of 9 years.I am just a begginier.so,please give me your feedback
Yours faithfully,
Mohit

Trouble Shooting Virtual Memory Problems

by jcbowen - 6/16/07 2:38 PM
In reply to: What do you mean, Windows Virtual Memory is too low?! by Lee Koo (ADMIN)
Well, Denise, virtual memory is a complex area touching at the very heart of your laptop's functionality, and I doubt that very many people understand all its ramifications. I certainly don't. Nevertheless, the problem frequently has a fairly simple solution. Let's take a look at your situation and hope that yours is one of the simpler cases.

First of all, what is virtual memory? Your laptop uses two kinds of memory for running programs and storing data that is currently in use, and these two kinds of memory together are what is called virtual memory. The first of these is RAM or random access memory, which is what we normally think of when we talk about a computer's memory. Your laptop probably has 256, 512, or 1024 megaBytes of RAM.

But you also have a second kind of memory which is actually nothing more than a file (called the pagefile) on your hard disk. By default, in XP, this file will be one and a half times the size of your RAM, so if you have 512 meg RAM your pagefile will most likely be approximately 750 meg. As memory is needed in running your laptop RAM is allocated first to do the job of storing your running programs and data. But eventually, since programs are so big these days, as more programs start up you eventually run out of RAM. At that point the operating system takes part of what is stored in RAM and writes it out to disk in the pagefile, thus freeing up RAM for additional requirements. The system tries to choose blocks of memory that are not frequently used to write to the pagefile and to keep in RAM those parts that are regularly accessed. But inevitably some of the data in the pagefile is needed by a running program, so it must be read from the pagefile on disk back into RAM, while some other block of data is written out to disk to make room for the needed data in RAM. This sounds, and is, complicated, but it's all going on many times a second, usually without a problem.

Unfortunately, you do have a problem and that is because for some reason your system is using up not only all the RAM but also the available space in the pagefile - in other words all the virtual memory (RAM and pagefile) are used and there is no memory left to meet new memory requests. There are two basic causes of this problem. Either (1) you simply do not have enough virtual memory to handle the current normal operation of your laptom, or (2) some process or processes on your computer are using up much more virtual memory than they should.

If the problem is insufficient virtual memory, the solution is to increase it by adding RAM, increasing the size of the pagefile or both. But if some process is using too much virtual memory, then the solution is identify the guilty process and either terminate or find a way to cause it to use less memory.

I hope you're still with me, Denise. This has been rather long on theory, but I think it's important to understand how things work if you're going to find and fix the problem. At least we're ready now to go looking for solutions!

First of all do you have enough virtual memory for all the tasks you are asking your laptop to carry out? The first half of that equation is how much RAM do you have. As I said earlier, it is most likely either 256, 512, or 1024 megaBytes. In general, 256 meg is simply not enough for all an XP system is asked to do today, and, if at all possible, you should bump your RAM up to at least 512 meg, which should be enough if you are mainly doing email, internet, some word processing and a few other odds and ends. On the other hand if you're doing something very memory intensive such as video editing, you probably need to be up to 1024 meg or more (and probably on something other than a laptop).

However, if you're short of RAM but are unwilling or unable to add more to your system, you can still up your overall virtual memory by increasing the size of your pagefile. To do this, open the System Properties window in the Control Panel. (In case you don't know how much RAM your laptop has, this is shown on the General Tab when the System Properties window opens.) But to get to the pagefile, click on the Advanced tab, then click Settings in the Performance box, then click Advanced in the Performance options. At the bottom you will see the current size of your pagefile. As I wrote earlier, this is normally one and a half times your RAM. But if you only have 256 meg of RAM, you need a bigger page file, so click on the Change button. Now select the customs size button and write in the size you want probably twice as large as it previously was. I'd recommend putting the same size in both the Intial Size and Maximum Size windows. Just make sure it's significantly more than you had before AND that you have enough free disk space to handle it. Once you click OK on all the open windows, you will probably have to restart your system, and then you'll be running with more virtual memory and hopefully a solved problem!

But maybe you decided you really already have a reasonable amount of virtual memory, so the problem is that some process is using too much of it! So let's see if we can find the culprit. Start by opening the Windows Task Manager, which can be done with the old 3 fingered salute of pressing Ctrl, Alt, and Delete keys all at the same time. Once this is opened, we want to look at two things. First click the Performance tab. You'll see first the CPU Usage and then the Page File Usage, which is what we're interested in. In the PF Usage window you will see how many megaBytes of the pagefile is currently in use. For instance on my system right now it says 479 MB. Since my pagefile is 1000 B I know it is about half full, so I still have plenty of virtual memory.

Now on the Task Manager click the Processes tab, make sure the slidebar on the right is all the way up, and click twice on the column name Mem Usage. This should sort the output by memory usage with the largest user on top. In my case the biggest user is firefox.exe using 37,144K. Okay, now just go about your normal computing, but leave the Task Manager window open. Periodically, click back to Performance tab and then the Processes Tab. As you approach running out of virtual memory, you will see the Pagefile size increasing, and you will see some process right at the top of the Process list using more and more memory. That's the culprit that's causing your problem! It might be a process you don't need and you can terminate it with the End Process button, and then do whatever is necessary to prevent it from running in the future.

But more likely it's a program you want, such as your browser or your photo editing program. You may simply be opening too may tabs in Firefox that are viewing pages with lots of graphics, or you may be trying to open too may photos in your editing program. My guess is that this is the most likely cause of your problem, and once you identify the program that's using all your virtual memory you can probably eliminate the problem simply by modifying how you use that program. If you don't recognize which program it is by its name in the Task Manager, read the answers to last week's question which tell you all about how to do that.

One other possibility for the culprit program is that is some program that has a bug in it that causes it to use more and more memory as long as it's running. If that should seem to be the case, the imediate solution (other than finding a different program for the job) is to simply exit and restart the program periodically. You should also check that program's web site to see if they have a fix for the bug!

One final thought (which maybe should have been the first one) is that it sounds as if your laptop was running fine for a long time, and then this problem started. In all probability you installed some new program or started using an old one much more heavily at that time, so that might be a clue to what is using all the memory. In the same vein, what program are you using when you run out of memory? If it's usually the same one, the problem is almost surely there