Oracle : Waitevents

select
substrb(vse.event,1,40) EVENT,
to_char(average_wait,'999,999,999.99') AVG_WAIT_SECS,
to_char(time_waited,'999,999,999') TIME_WAITED
from v$system_event vse
where vse.event != 'Null event'
and vse.event not like '%timer%'
and vse.event not like 'SQL*Net%'
and 15 > (
  select count(*) from v$system_event vse2
  where vse2.time_waited > vse.time_waited
  and vse2.event != 'Null event'
  and vse2.event not like '%timer%'
  and vse2.event not like 'SQL*Net%' )
order by vse.time_waited desc
/