Step 2 : Time analysis on SQL Stats shows high PL/SQL execution time
The assumption that the elapsed time is the sum of other subcomponents doesn’t hold well here.
Oracle double counted PL/SQL execution time as part of CPU time.
Step 3 : Check SQL text and identify the problem PL/SQL function
As we can see here, a PL/SQL function was applied to all rows in the data set.
Due to the fact that the data set contained a large amount of data, the usage of PL/SQL function caused a considerable amount of CPU time.