Compare Period ADDM (supported for any Oracle database Target of version 10.2.0.4 and higher) is another new feature related to ADDM in this new version. This helps in comparative performance analysis. For example, you may have noticed that the performance of your database is worse on some days and better on other days—and you want to know the reason for this. Are some other batch programs running on some days?
Or, you have a RAC database and some instances are faster and you want to know if the workload is unevenly distributed. If any changes have been made across those periods, that is also important to understand.
You access this feature by going to Performance | AWR | Compare Period ADDM.
This will take two AWR snapshot periods ...