Performance - Locks DML

• Show sessions that are blocking each other
• Show locked objects
• Show which row is locked
• List locks

Show sessions that are blocking each other

select 'SID ' || l1.sid ||' is blocking  ' || l2.sid blocking
from v$lock l1, v$lock l2
where l1.block =1 and l2.request > 0
and l1.id1=l2.id1
and l1.id2=l2.id2
/

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
/

Show 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
/

Then select the row with that rowid...
select * from <table> where rowid=<rowid>;




List 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')
/