In AWR, the ‘Instance CPU’ table comes under the ‘Report Summary’ section. Refer to the below figure:
To analyse the ‘Instance CPU’ section, you must Look at the Host CPU and Instance CPU sections. The key things to look for are the values “%Idle” in the “Host CPU” section and “%Total CPU” in the “Instance CPU” section.
If the “%Idle” is low and “%Total CPU” is high then the instance could have a CPU bottleneck (be CPU constrained). Otherwise, the high DB CPU usage just means that the database spends a lot of time in CPU (processing) compared to I/O and other events. In either case (CPU is a bottleneck or not) there could be individual expensive SQLs with high CPU time, which could indicate suboptimal execution plans, especially if accompanied by high (buffer) gets.
You may be interested:
- AWR – Buffer Hit Ratio – Analysis
- AWR – Execute to Parse Ratio – Analysis
- AWR – Instance Efficiency Percentages
- AWR Report Analysis Guide