Memory capacity becomes a problem when all of the processes running on the Windows NT server (including Windows NT itself) need more code or data pages than provided for by physical memory in the computer. At that point, the operating system temporarily stores some memory pages on the local disk in order to make more memory available for the next service. As memory contention increases, the system eventually reaches a point where the paging activity (which is using system resources such as CPU cycles, bus bandwidth, and disk access time) is using more resources than the actual work. This is often called "thrashing."
Thrashing can be viewed as a contention for memory. As with most resources, some contention is tolerable. However, as memory contention increases, response times typically increase exponentially.
If memory is a performance bottleneck, you can:
Tip There is another optimization you can make that affects how your server uses memory and paging files. This parameter is found in the Windows Control Panel System application. To access it, click the Start menu, point to Settings, and then click Control Panel. In the Control Panel, double-click the System icon, and then click the Performance tab. You should configure the Virtual Memory to have a large paging file. It is very difficult to determine exactly how large the paging file should be, but a good rule of thumb is to choose 125MB plus the available RAM. For example, if you have 64 MB of RAM in your server, you would set the paging file size to be (125+64) MB or 189 MB.
Note You can easily monitor memory use by using the Windows NT Performance Monitor. For more information, see Using Performance Monitor in this chapter.