This is not the right way to cancel a request!!!
It is locked because the concurrent manager process is holding it.
You should cancel it from the application either using the owner's account or from System Administrator responsibility.
Yes that is what I did first, but it can not lock due to same reason
What is causing the lock?
I told you!
It is locked since the request is running.
I killed the holder,
L.OBJECT_ID = O.OBJECT_ID
AND L.SESSION_ID = S.SID
AND S.PADDR = P.ADDR
AND S.SQL_ADDRESS = SQ.ADDRESS;