3. Last 30 minutes result those resources that are in high demand on your system.

select active_session_history.event,
sum(active_session_history.wait_time +
active_session_history.time_waited) total_wait_time
from v$active_session_history active_session_history
where active_session_history.sample_time between sysdate - 60/2880 and sysdate
group by active_session_history.event
order by 2;