The below query can be used for determining the if any object locked in an oracle database.
select c.owner, c.object_name, c.object_type, b.sid, b.serial#,
b.status, b.osuser, b.machine
from
v$locked_object a , v$session b, dba_objects c
where
b.sid = a.session_id
and a.object_id = c.object_id;
And if you need to kill any session you can use the below query to do the same.
alter system kill session sid,serial;