How to Find LOCKS / blocking sessions :

Show locked objects
set lines 100 pages 999
col username  format a20
col sess_id  format a10
col object format a25
col mode_held format a10
select oracle_username || ‘ (‘ || s.osuser || ‘)’ username
, s.sid || ‘,’ || s.serial# sess_id
, owner || ‘.’ || object_name object
, object_type
, decode( l.block
, 0, ‘Not Blocking’
, 1, ‘Blocking’
, 2, ‘Global’) status
, decode(v.locked_mode
, 0, ‘None’
, 1, ‘Null’
, 2, ‘Row-S (SS)’
, 3, ‘Row-X (SX)’
, 4, ‘Share’
, 5, ‘S/Row-X (SSX)’
, 6, ‘Exclusive’, TO_CHAR(lmode)) mode_held
from v$locked_object v
, dba_objects d
, v$lock l
, v$session s
where  v.object_id = d.object_id
and  v.object_id = l.id1
and  v.session_id = s.sid
order by oracle_username
, session_id;
Find Which ROW is locked :
select do.object_name
, row_wait_obj#
, row_wait_file#
, row_wait_block#
, row_wait_row#
, dbms_rowid.rowid_create (1, ROW_WAIT_OBJ#, ROW_WAIT_FILE#,
ROW_WAIT_BLOCK#, ROW_WAIT_ROW#)
from v$session s
, dba_objects do
where sid=&sid
and  s.ROW_WAIT_OBJ# = do.OBJECT_ID;
List of Locks:
column lock_type format a12
column mode_held format a10
column mode_requested format a10
column blocking_others format a20
column username format a10
SELECT session_id
, lock_type
, mode_held
, mode_requested
, blocking_others
, lock_id1
FROM dba_lock l
WHERE  lock_type NOT IN (‘Media Recovery’, ‘Redo Thread’)
SELECT DISTINCT a.sid “BLOCKED”, a.serial# “BLOCKEDSERIAL”, a.username “BLOCKEDUSER”, d.sid “BLOCKEDBYSID”,
d.serial# “BLOCKEDBYSERIAL#”, d.username “BLOCKINGUSERNAME”
from v$session a, dba_objects b, dba_data_files c, v$lock e,
(SELECT b.sid, b.serial#, b.username, a.id1
from v$lock a, v$session b where block=1
and a.sid=b.sid) d
where a.row_wait_obj#=b.object_id
and a.row_wait_file#=c.file_id
and a.lockwait is not null
and e.id1=d.id1
and e.block=0 and e.type=’TX’;

Script to Kill all the locks:

SELECT OS_USER_NAME, ORACLE_USERNAME AS orauser, s.sid, o.object_name,
o.object_type, s.serial#, a.sql_text
FROM v$locked_object l, dba_objects o, v$session s, v$sqlarea a
WHERE l.object_id = o.object_id
AND s.SQL_ADDRESS = a.address
AND l.SESSION_ID = s.sid;
SELECT ‘ALTER SYSTEM KILL SESSION ”’||TO_CHAR(s.sid)||’,’||TO_CHAR(s.serial#)||”’;’
AS “Statement to kill”
FROM v$locked_object l, dba_objects o, v$session s
WHERE l.object_id = o.object_id
AND l.SESSION_ID = s.sid;

Thanks
Srini