CPU usage Database Performance

An Oracle instance consists of a number of background processes. These background processes (pmon, smon, dbwr) are executing programs within the OS, and they require CPU services in order to perform their requested tasks. Demand for the CPU within the OS is a very important external influence on Oracle database tuning. Only one process may use the CPU at any given instance, and the OS has a method for slicing processes, and giving the illusion of multiprocessing. Many hosts contain multiple CPUs (e.g., SMP and MPP systems), but these also only allow one task to use the CPU at any time.