Blocking locks by user

select /*+ ORDERED */
blocker.sid blocker_sid
, waiting.sid waiting_sid
, TRUNC(waiting.ctime/60) min_waiting
, waiting.request
from (select *
from v$lock
where block != 0
and type = 'TX') blocker
, v$lock waiting
where waiting.type='TX'
and waiting.block = 0
and waiting.id1 = blocker.id1