Locks

Processes Waiting on Locks

-- Processes Waiting on Locks
SELECT
   holding_session bsession_id,
   b.username busername,
   b.machine bmachine,
   waiting_session wsession_id,
   a.username wusername,
   a.machine wmachine,
   c.lock_type type,
   mode_held,
   mode_requested,
   lock_id1,
   lock_id2,
   b.machine
FROM
   sys.v_$session b,
   sys.dba_waiters c,
   sys.v_$session a
WHERE
   c.holding_session=b.sid
   and
   c.waiting_session=a.sid;

Blockers

-- Blockers
SELECT
   a.session_id,
   b.username,
   b.machine,
   type,
   mode_held,
   mode_requested,
   lock_id1,
   lock_id2
FROM
   sys.v_$session b,
   sys.dba_blockers c,
   sys.dba_lock a
WHERE
   c.holding_session=a.session_id
   AND
   c.holding_session=b.sid;

Transaction Enqueues

What is normal? Note the CTIME for this query. It is time in seconds since the last mode change for the transaction. The number is updated by PMON so it may lag a little, but if there is a transaction that has been waiting for more than a few seconds (10-15) it may need a closer look. Transactions waiting more than 60 seconds definitely need a closer look! If you query this multiple times, you should see the transactions progress and then disappear once they are done.
-- Transaction Enqueues
select V$TRANSACTION_ENQUEUE.*, v$session.username, v$session.machine
From V$TRANSACTION_ENQUEUE, v$session
where V$TRANSACTION_ENQUEUE.SID = v$session.SID
order by ctime desc;

Report on All DML Locks Held

-- Report on All DML Locks Held
SELECT
   NVL(owner,'SYS') owner,
   session_id,
   name,
   mode_held,
   mode_requested
FROM
   sys.dba_dml_locks
ORDER BY 2;

Report on all DDL Locks Held

SELECT
   NVL(owner,'SYS') owner, 
   session_id,

Jared Still's showlock.sql script

Original post here.
-- showlock.sql - show all user locks
--
-- see ML Note 1020008.6 for fully decoded locking script
-- parts of the that script to not work correctly, but the
-- lock types are current
-- (script doesn't find object that is locked )
--
-- speeded up greatly by changing order of where clause,
-- jks 04/09/1997 - show lock addresses and lockwait

-- jks 04/09/1997 - outer join on all_objects
-- encountered situation on 7.2
-- where there was a lock with no
-- matching object_id
-- jks 02/24/1999 - join to dba_waiters to show waiters and blockers
-- jkstill 05/22/2006 - revert back to previous version without tmp tables
-- update lock info
-- add lock_description and rearrange output
-- jkstill 04/28/2008 - added command column
-- updated lock types
-- removed one outer join by using inline view on sys.user$
-- jkstill 04/28/2008 - added subquery factoring
-- converted to ANSI joins
-- changed alias for v$lock to l and v$session to s

set trimspool on
ttitle off
set linesize 150
set pagesize 60
column command format a15
column osuser heading 'OS|Username' format a7 truncate
column process heading 'OS|Process' format a7 truncate
column machine heading 'OS|Machine' format a10 truncate
column program heading 'OS|Program' format a18 truncate
column object heading 'Database|Object' format a25 truncate
column lock_type heading 'Lock|Type' format a4 truncate
column lock_description heading 'Lock Description'format a16 truncate
column mode_held heading 'Mode|Held' format a15 truncate
column mode_requested heading 'Mode|Requested' format a10 truncate
column sid heading 'SID' format 999
column username heading 'Oracle|Username' format a7 truncate
column image heading 'Active Image' format a20 truncate
column sid format 99999
col waiting_session head 'WATR' format 9999
col holding_session head 'BLKR' format 9999

with dblocks as (
select /*+ ordered */
l.kaddr,
s.sid,
s.username,
lock_waiter.waiting_session,
lock_blocker.holding_session,
(
select name
from sys.user$
where user# = o.owner#
) ||'.'||o.name
object,
decode(command,
0,'BACKGROUND',
1,'Create Table',
2,'INSERT',
3,'SELECT',
4,'CREATE CLUSTER',
5,'ALTER CLUSTER',
6,'UPDATE',
7,'DELETE',
8,'DROP',
9,'CREATE INDEX',
10,'DROP INDEX',
11,'ALTER INDEX',
12,'DROP TABLE',
13,'CREATE SEQUENCE',
14,'ALTER SEQUENCE',
15,'ALTER TABLE',
16,'DROP SEQUENCE',
17,'GRANT',
18,'REVOKE',
19,'CREATE SYNONYM',
20,'DROP SYNONYM',
21,'CREATE VIEW',
22,'DROP VIEW',
23,'VALIDATE INDEX',
24,'CREATE PROCEDURE',
25,'ALTER PROCEDURE',
26,'LOCK TABLE',
27,'NO OPERATION',
28,'RENAME',
29,'COMMENT',
30,'AUDIT',
31,'NOAUDIT',
32,'CREATE EXTERNAL DATABASE',
33,'DROP EXTERNAL DATABASE',
34,'CREATE DATABASE',
35,'ALTER DATABASE',
36,'CREATE ROLLBACK SEGMENT',
37,'ALTER ROLLBACK SEGMENT',
38,'DROP ROLLBACK SEGMENT',
39,'CREATE TABLESPACE',
40,'ALTER TABLESPACE',
41,'DROP TABLESPACE',
42,'ALTER SESSION',
43,'ALTER USER',
44,'COMMIT',
45,'ROLLBACK',
46,'SAVEPOINT',
47,'PL/SQL EXECUTE',
48,'SET TRANSACTION',
49,'ALTER SYSTEM SWITCH LOG',
50,'EXPLAIN',
51,'CREATE USER',
52,'CREATE ROLE',
53,'DROP USER',
54,'DROP ROLE',
55,'SET ROLE',
56,'CREATE SCHEMA',
57,'CREATE CONTROL FILE',
58,'ALTER TRACING',
59,'CREATE TRIGGER',
60,'ALTER TRIGGER',
61,'DROP TRIGGER',
62,'ANALYZE TABLE',
63,'ANALYZE INDEX',
64,'ANALYZE CLUSTER',
65,'CREATE PROFILE',
66,'DROP PROFILE',
67,'ALTER PROFILE',
68,'DROP PROCEDURE',
69,'DROP PROCEDURE',
70,'ALTER RESOURCE COST',
71,'CREATE SNAPSHOT LOG',
72,'ALTER SNAPSHOT LOG',
73,'DROP SNAPSHOT LOG',
74,'CREATE SNAPSHOT',
75,'ALTER SNAPSHOT',
76,'DROP SNAPSHOT',
79,'ALTER ROLE',
85,'TRUNCATE TABLE',
86,'TRUNCATE CLUSTER',
87,'-',
88,'ALTER VIEW',
89,'-',
90,'-',
91,'CREATE FUNCTION',
92,'ALTER FUNCTION',
93,'DROP FUNCTION',
94,'CREATE PACKAGE',
95,'ALTER PACKAGE',
96,'DROP PACKAGE',
97,'CREATE PACKAGE BODY',
98,'ALTER PACKAGE BODY',
99,'DROP PACKAGE BODY',
command||'-UNKNOWN'
) COMMAND,
l.type lock_type,
decode
(
l.type,
'BL','Buffer hash table instance lock',
'CF',' Control file schema global enqueue lock',
'CI','Cross-instance function invocation instance lock',
'CS','Control file schema global enqueue lock',
'CU','Cursor bind lock',
'DF','Data file instance lock',
'DL','Direct loader parallel index create',
'DM','Mount/startup db primary/secondary instance lock',
'DR','Distributed recovery process lock',
'DX','Distributed transaction entry lock',
'FI','SGA open-file information lock',
'FS','File set lock',
'HW','Space management operations on a specific segment lock',
'IN','Instance number lock',
'IR','Instance recovery serialization global enqueue lock',
'IS','Instance state lock',
'IV','Library cache invalidation instance lock',
'JQ','Job queue lock',
'KK','Thread kick lock',
'LA','Library cache lock instance lock (A=namespace)',
'LB','Library cache lock instance lock (B=namespace)',
'LC','Library cache lock instance lock (C=namespace)',
'LD','Library cache lock instance lock (D=namespace)',
'LE','Library cache lock instance lock (E=namespace)',
'LF','Library cache lock instance lock (F=namespace)',
'LG','Library cache lock instance lock (G=namespace)',
'LH','Library cache lock instance lock (H=namespace)',
'LI','Library cache lock instance lock (I=namespace)',
'LJ','Library cache lock instance lock (J=namespace)',
'LK','Library cache lock instance lock (K=namespace)',
'LL','Library cache lock instance lock (L=namespace)',
'LM','Library cache lock instance lock (M=namespace)',
'LN','Library cache lock instance lock (N=namespace)',
'LO','Library cache lock instance lock (O=namespace)',
'LP','Library cache lock instance lock (P=namespace)',
'LS','Log start/log switch enqueue lock',
'MB','Master buffer hash table instance lock',
'MM','Mount definition gloabal enqueue lock',
'MR','Media recovery lock',
'PA','Library cache pin instance lock (A=namespace)',
'PB','Library cache pin instance lock (B=namespace)',
'PC','Library cache pin instance lock (C=namespace)',
'PD','Library cache pin instance lock (D=namespace)',
'PE','Library cache pin instance lock (E=namespace)',
'PF','Library cache pin instance lock (F=namespace)',
'PF','Password file lock',
'PG','Library cache pin instance lock (G=namespace)',
'PH','Library cache pin instance lock (H=namespace)',
'PI','Library cache pin instance lock (I=namespace)',
'PI','Parallel operation lock',
'PJ','Library cache pin instance lock (J=namespace)',
'PK','Library cache pin instance lock (L=namespace)',
'PL','Library cache pin instance lock (K=namespace)',
'PM','Library cache pin instance lock (M=namespace)',
'PN','Library cache pin instance lock (N=namespace)',
'PO','Library cache pin instance lock (O=namespace)',
'PP','Library cache pin instance lock (P=namespace)',
'PQ','Library cache pin instance lock (Q=namespace)',
'PR','Library cache pin instance lock (R=namespace)',
'PR','Process startup lock',
'PS','Library cache pin instance lock (S=namespace)',
'PS','Parallel operation lock',
'PT','Library cache pin instance lock (T=namespace)',
'PU','Library cache pin instance lock (U=namespace)',
'PV','Library cache pin instance lock (V=namespace)',
'PW','Library cache pin instance lock (W=namespace)',
'PX','Library cache pin instance lock (X=namespace)',
'PY','Library cache pin instance lock (Y=namespace)',
'PZ','Library cache pin instance lock (Z=namespace)',
'QA','Row cache instance lock (A=cache)',
'QB','Row cache instance lock (B=cache)',
'QC','Row cache instance lock (C=cache)',
'QD','Row cache instance lock (D=cache)',
'QE','Row cache instance lock (E=cache)',
'QF','Row cache instance lock (F=cache)',
'QG','Row cache instance lock (G=cache)',
'QH','Row cache instance lock (H=cache)',
'QI','Row cache instance lock (I=cache)',
'QJ','Row cache instance lock (J=cache)',
'QK','Row cache instance lock (L=cache)',
'QL','Row cache instance lock (K=cache)',
'QM','Row cache instance lock (M=cache)',
'QN','Row cache instance lock (N=cache)',
'QO','Row cache instance lock (O=cache)',
'QP','Row cache instance lock (P=cache)',
'QQ','Row cache instance lock (Q=cache)',
'QR','Row cache instance lock (R=cache)',
'QS','Row cache instance lock (S=cache)',
'QT','Row cache instance lock (T=cache)',
'QU','Row cache instance lock (U=cache)',
'QV','Row cache instance lock (V=cache)',
'QW','Row cache instance lock (W=cache)',
'QX','Row cache instance lock (X=cache)',
'QY','Row cache instance lock (Y=cache)',
'QZ','Row cache instance lock (Z=cache)',
'RE','USE_ROW_ENQUEUE enforcement lock',
'RT','Redo thread global enqueue lock',
'RW','Row wait enqueue lock',
'SC','System commit number instance lock',
'SH','System commit number high water mark enqueue lock',
'SM','SMON lock',
'SN','Sequence number instance lock',
'SQ','Sequence number enqueue lock',
'SS','Sort segment lock',
'ST','Space transaction enqueue lock',
'SV','Sequence number value lock',
'TA','Generic enqueue lock',
'TD','DDL enqueue lock',
'TE','Extend-segment enqueue lock',
'TM','DML enqueue lock',
'TO','Temporary Table Object Enqueue',
'TS',decode(l.id2,
0,'Temporary segment enqueue lock (ID2=0)',
1,'New block allocation enqueue lock (ID2=1)',
'UNKNOWN!'
),
'TT','Temporary table enqueue lock',
'TX','Transaction enqueue lock',
'UL','User supplied lock',
'UN','User name lock',
'US','Undo segment DDL lock',
'WL','Being-written redo log instance lock',
'WS','Write-atomic-log-switch global enqueue lock',
'UNKOWN'
) lock_description,
decode
(
l.lmode,
0, 'None', /* Mon Lock equivalent */
1, 'No Lock', /* N */
2, 'Row-S (SS)', /* L */
3, 'Row-X (SX)', /* R */
4, 'Share', /* S */
5, 'S/Row-X (SRX)', /* C */
6, 'Exclusive', /* X */
to_char(l.lmode)
) mode_held,
decode
(
l.request,
0, 'None', /* Mon Lock equivalent */
1, 'No Lock', /* N */
2, 'Row-S (SS)', /* L */
3, 'Row-X (SX)', /* R */
4, 'Share', /* S */
5, 'S/Row-X (SSX)', /* C */
6, 'Exclusive', /* X */
to_char(l.request)
) mode_requested,
s.osuser,
s.machine,
s.program,
s.process
from
v$lock l
join v$session s on s.sid = l.sid
left outer join sys.dba_waiters lock_blocker on lock_blocker.waiting_session = s.sid
left outer join sys.dba_waiters lock_waiter on lock_waiter.holding_session = s.sid
left outer join sys.obj$ o on o.obj# = l.id1
where s.type != 'BACKGROUND'
)
select
--kaddr,
sid,
username,
waiting_session,
holding_session,
object,
command,
lock_type,
lock_description,
mode_held,
mode_requested,
--osuser,
--machine,
program,
process
from dblocks
order by sid, object
/