CPU usage and memory usage

Hi,       Is there any dictionary view to get the CPU usage and memory usage by the Oracle sessions in a given specific range of date/time.

In production, few applications face preformance issues, CPU usage cross 70 or 80 or even 90 in some DB servers etc. So, we plan to get the CPU usage and memory usage for all the databases to identify if any tuning or hardware upgrade is required.

     I am planning to do as below,

Say for example, if the DB server has 2 dual core CPU which will be equal to 4 CPU. So, in the business hours, ie from 08:00 to 18:00, the time is 10 hours. So, max CPU time can be 40 hours (10 hours * 4 CPU) in this duration.