ASH Script for Finding out Top Wait Events in Oracle

prompt ************************************
prompt **** ASH OVERALL WAIT PROFILE
prompt ************************************
set lines 999
SELECT MIN(sample_time) min_ash_available,sysdate-MIN(sample_time) available duration FROM v$active_session_history;
select * from (
select NVL(event,'CPU') event,count(*),
round((ratio_to_report(sum(1)) over ()*100),1) rr
from gv$active_session_history
WHERE user_id0
AND sample_timetrunc(sysdate-1)
group by event
order by 2 desc
) where rownum<10;