enq: TX - row lock contention

Find your blocking session with the following query

Select v.sid,s.blocking_session, s.event, v.type,v.lmode,v.request,o.object_name, o.object_type
from v$lock v ,dba_objects o, v$session s
where v.id1 = o.object_id
and v.sid = s.sid
and event = 'enq: TX - row lock contention'

You can get the blocking session details from

select * from v$session where sid =<blocking_session from above query>;

Then kill the session

Alter system Kill session 'SID,SERIAL#'