The working set of a program is a collection of those pages in its virtual address space that have been recently referenced. It includes both shared and private data. The shared data includes pages that contain all instructions your application executes, including those in your DLLs and the system DLLs. As the working set size increases, memory demand increases.
The Working Set Tuner (WST) can help you reduce the amount of space your program takes in RAM. You should tune your application's working set even if you are satisfied with its performance. Your program will coexist with other running applications, so it's a good idea to save space. The Windows NT code itself has been tuned with WST.
Even if you are not concerned about the RAM your applications takes away from other applications, you probably care about the time it takes to load your own program into RAM from disk. WST can help with that too.
WST can improve the speed of your program in another way. It can reduce the space your application requires in the processor cache and the translation buffer (another processor cache used for page translation). Not only will your application code execute faster, it will interfere less with the code in Windows NT.
At the end of this overview, we'll also describe how to use the VADump tool, which lets you look inside your application's working set.