SQL queries which are using CPU resources

select
ss.username,
ss.serial#,
se.SID,
VALUE/100 cpu_usage_seconds
from
v$session ss,
v$sesstat se,
v$statname sn
where
se.STATISTIC# = sn.STATISTIC#
and
NAME like '%CPU used by this session%'
and
se.SID = ss.SID
and
ss.status='ACTIVE'
and
ss.username is not null
order by VALUE desc;