Oracle Wait activity depending on there wait class

select
wait_class,
total_waits,
round(100 * (total_waits / sum_waits), 2) pct_waits,
round((time_waited / 100), 2) time_waited_secs,
round(100 * (time_waited / sum_time), 2) pct_time
from
  (select
        wait_class,
        total_waits,
        time_waited
  from
        v$system_wait_class
  where
        wait_class != 'Idle'),
  (select
        sum(total_waits) sum_waits,
        sum(time_waited) sum_time
  from
        v$system_wait_class
  where
        wait_class != 'Idle')
order by 5 desc;

Summary of waits depending on wait class.
10g wait class identifier makes the identification of wait behavior easier. 
Wait events are grouped into different classes.