Could you please explain when we should use ASH report.
The ASH comprises recent information on active sessions sampled every second, and the name of this report describes the primary difference between it and AWR.
The AWR is taken every hour, and it will not aid in identifying issues that are currently on the database if it is one hour old.
In order to quickly fix database issues, detailed information from the last 5 to 10 minutes is usually required because it is costly to record session activity.
ASH samples V$SESSION every second and records the event for which the session is waiting.
Check this article for details on Oracle ADDM Report:
Thank you :)