Originally posted by ora_inf
I have 8 session are ruuning diff. sqls then why are they using only two CPUs?
Because those two processors are not even close to being heavily loaded by those 8 sessions, I suppose. What is the CPU usage of those two processor when those 8 sessions are running? I guess not even close to 100% - am I right?

Only when those two processes will be under heavy load will the OS (not Oracle) unburden them by using other available processor(s). It is cheaper and more efficient in terms of resources that way.