Show Top Wait Events Since Instance Startup

col event format a60

select event, total_waits, time_waited

from v$system_event e, v$event_name n

where n.event_id = e.event_id

and n.wait_class !='Idle'

and n.wait_class = (select wait_class from v$session_wait_class

 where wait_class !='Idle'

 group by wait_class having

sum(time_waited) = (select max(sum(time_waited)) from v$session_wait_class

where wait_class !='Idle'

group by (wait_class))) order by 3;