The Virtual Processors Layer
Database server processes are called virtual processors because the way they function is similar to the way that a CPU functions in a computer. Just as a CPU runs multiple operating-system processes to service multiple users, a database server virtual processor runs multiple threads to service multiple SQL client applications. Virtual processors are divided into classes depending upon the type of processing that they do. Each class of virtual processor is dedicated to processing certain types of threads.
This layer monitors every virtual processor class to report the number of processors associated with it and their collective CPU usage, so that CPU-intensive classes can be quickly determined.
Figure 1 : The tests associated with the Virtual Processors layer