Private Oracle Area - Oracle.Locks

ALL_WM_LOCKED_TABLES	GV$LOCK_TYPE
DBA_BLOCKERS	GV$_LOCK
DBA_DDL_LOCKS	USER_WM_LOCKED_TABLES
DBA_DML_LOCKS	V_$DLM_ALL_LOCKS
DBA_LOCK	V_$DLM_LOCKS
DBA_LOCK_INTERNAL	V_$GLOBAL_BLOCKED_LOCKS
DBMS_LOCK	V_$LOCK
DBMS_LOCK_ALLOCATED (table)	V_$LOCKED_OBJECT
GV$DLM_ALL_LOCKS	V_$LOCKS_WITH_COLLISIONS
GV$DLM_LOCKS	V_$LOCK_ACTIVITY
GV$GLOBAL_BLOCKED_LOCKS	V_$LOCK_ELEMENT
GV$LOCK	V_$LOCK_TYPE
GV$LOCKED_OBJECT	V_$_LOCK
GV$LOCKS_WITH_COLLISIONS	WM$ALL_LOCKS_VIEW
GV$LOCK_ACTIVITY	WM$LOCKROWS_INFO
GV$LOCK_ELEMENT	WM$LOCKROWS_INFO_IDX

Lock Definitions

Descriptions

Name	Description
sub-share	Can be used on an aggregate object to indicate that share locks are being aquired on sub-parts of the object.
sub-exclusive	Can be used on an aggregate object to indicate that exclusive locks are being aquired on sub-parts of the object.
share-sub-exclusive	Indicates that the entire aggregate object has a share lock, but some of the sub-parts may additionally have exclusive locks.

Lock Escalation

How to make lock escalation look good

Subject: Re: How to make lock escalation look good...
Date: Wed, 21 May 2003 14:03:35 GMT
From: "Jim Kennedy"
Newsgroups: comp.databases.oracle.server

I've worked with DB2 and it requires throwing most transactions out the window. Worse than that dynamic sql MUST be followed immediately by a commit or no one else can do one. (their query tool does this for you) DB2 does NOT do dynamic sql; it does static sql. What it does with "dynamic" sql is create a plan and bind it in then run it - turning dynamic to static and that puts a lock on the plan table until you commit. So anyone else running dynamic sql can't until you commit. (plan table is a source of serialization for the entire system). When I worked with it (DB2 on a mainframe) we had to make sure all DML had a commit immediately after it.

Lock Demo

Locking Demo

Session 1	Session 2
conn / as sysdba	conn scott/tiger
	UPDATE emp SET deptno=deptno+10 WHERE deptno < 40;
SELECT username, gv$lock.sid, TRUNC(id1/power(2,16)) rbs, BITAND(id1,TO_NUMBER('ffff','xxxx'))+0 slot, id2 seq, lmode, request FROM gv$lock, gv$session WHERE gv$lock.type = 'TX' AND gv$lock.sid = gv$session.sid AND gv$session.username = 'SCOTT'; SELECT XIDUSN, XIDSLOT, XIDSQN FROM gv$transaction;
	rollback;

Lock Table

Table Locking

LOCK TABLE IN MODE [NOWAIT | WAIT ];

LOCK TABLE uwclass.servers IN exclusive MODE WAIT 120;

Lock Related Queries

Active Table Locks

SELECT SUBSTR(a.object,1,25) TABLENAME,
SUBSTR(s.username,1,15) USERNAME,
SUBSTR(p.pid,1,5) PID,
SUBSTR(p.spid,1,10) SYSTEM_ID,
DECODE(l.type,
'RT','Redo Log Buffer',
'TD','Dictionary',
'TM','DML',
'TS','Temp Segments',
'TX','Transaction',
'UL','User',
'RW','Row Wait',
l.type) LOCK_TYPE
FROM gv$access a, gv$process p, gv$session s, gv$lock l
WHERE s.sid = a.sid
AND s.paddr = p.addr
AND l.sid = p.pid
GROUP BY a.object, s.username, p.pid, l.type, p.spid
ORDER BY a.object, s.username;

Active Locks

SELECT s.username, s.sid, s.serial#, s.osuser, k.ctime, o.object_name
object, k.kaddr, DECODE(l.locked_mode,
1, 'No Lock',
2, 'Row Share',
3, 'Row Exclusive',
4, 'Shared Table',
5, 'Shared Row Exclusive',
6, 'Exclusive') locked_mode,
DECODE(k.type,
'BL','Buffer Cache Management (PCM lock)',
'CF','Controlfile Transaction',
'CI','Cross Instance Call',
'CU','Bind Enqueue',
'DF','Data File',
'DL','Direct Loader',
'DM','Database Mount',
'DR','Distributed Recovery',
'DX','Distributed Transaction',
'FS','File Set',
'IN','Instance Number',
'IR','Instance Recovery',
'IS','Instance State',
'IV','Library Cache Invalidation',
'JQ','Job Queue',
'KK','Redo Log Kick',
'LA','Library Cache Lock',
'LB','Library Cache Lock',
'LC','Library Cache Lock',
'LD','Library Cache Lock',
'LE','Library Cache Lock',
'LF','Library Cache Lock',
'LG','Library Cache Lock',
'LH','Library Cache Lock',
'LI','Library Cache Lock',
'LJ','Library Cache Lock',
'LK','Library Cache Lock',
'LL','Library Cache Lock',
'LM','Library Cache Lock',
'LN','Library Cache Lock',
'LO','Library Cache Lock',
'LP','Library Cache Lock',
'MM','Mount Definition',
'MR','Media Recovery',
'NA','Library Cache Pin',
'NB','Library Cache Pin',
'NC','Library Cache Pin',
'ND','Library Cache Pin',
'NE','Library Cache Pin',
'NF','Library Cache Pin',
'NG','Library Cache Pin',
'NH','Library Cache Pin',
'NI','Library Cache Pin',
'NJ','Library Cache Pin',
'NK','Library Cache Pin',
'NL','Library Cache Pin',
'NM','Library Cache Pin',
'NN','Library Cache Pin',
'NO','Library Cache Pin',
'NP','Library Cache Pin',
'NQ','Library Cache Pin',
'NR','Library Cache Pin',
'NS','Library Cache Pin',
'NT','Library Cache Pin',
'NU','Library Cache Pin',
'NV','Library Cache Pin',
'NW','Library Cache Pin',
'NX','Library Cache Pin',
'NY','Library Cache Pin',
'NZ','Library Cache Pin',
'PF','Password File',
'PI','Parallel Slaves',
'PR','Process Startup',
'PS','Parallel Slave Synchronization',
'QA','Row Cache Lock',
'QB','Row Cache Lock',
'QC','Row Cache Lock',
'QD','Row Cache Lock',
'QE','Row Cache Lock',
'QF','Row Cache Lock',
'QG','Row Cache Lock',
'QH','Row Cache Lock',
'QI','Row Cache Lock',
'QJ','Row Cache Lock',
'QK','Row Cache Lock',
'QL','Row Cache Lock',
'QM','Row Cache Lock',
'QN','Row Cache Lock',
'QO','Row Cache Lock',
'QP','Row Cache Lock',
'QQ','Row Cache Lock',
'QR','Row Cache Lock',
'QS','Row Cache Lock',
'QT','Row Cache Lock',
'QU','Row Cache Lock',
'QV','Row Cache Lock',
'QW','Row Cache Lock',
'QX','Row Cache Lock',
'QY','Row Cache Lock',
'QZ','Row Cache Lock',
'RT','Redo Thread',
'SC','System Commit number',
'SM','SMON synchronization',
'SN','Sequence Number',
'SQ','Sequence Enqueue',
'SR','Synchronous Replication',
'SS','Sort Segment',
'ST','Space Management Transaction',
'SV','Sequence Number Value',
'TA','Transaction Recovery',
'TM','DML Enqueue',
'TS','Table Space (or Temporary Segment)',
'TT','Temporary Table',
'TX','Transaction',
'UL','User-defined Locks',
'UN','User Name',
'US','Undo segment Serialization',
'WL','Writing redo Log',
'XA','Instance Attribute Lock',
'XI','Instance Registration Lock') type
FROM gv$session s, sys.gv$lock c, sys.gv$locked_object l,
dba_objects o, sys.gv$lock k, gv$lock v
WHERE o.object_id = l.object_id
AND l.session_id = s.sid
AND k.sid = s.sid
AND s.saddr = c.saddr
AND k.kaddr = c.kaddr
AND k.kaddr = v.kaddr
AND v.saddr = s.saddr
AND k.lmode = l.locked_mode
AND k.lmode = c.lmode
AND k.request = c.request
ORDER BY object;

List Locks

set wrap off
col lock_type format a12
col mode_held format a10
col mode_requested format a10
col blocking_others format a20
col 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');

Locked Objects

SELECT oracle_username USERNAME, owner OBJECT_OWNER,
object_name, object_type, s.osuser,
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 gv$locked_object v, dba_objects d,
gv$lock l, gv$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;

Locked Objects

SELECT o.owner, o.object_name, o.object_type, o.last_ddl_time, o.status, l.session_id, l.oracle_username, l.locked_mode
FROM dba_objects o, gv$locked_object l
WHERE o.object_id = l.object_id;

Locked Objects

SELECT DECODE(request,0,'Holder: ','Waiter:') || sid sess, id1, id2, lmode, request, type
FROM gv$lock
WHERE (id1, id2, type) IN (
SELECT id1, id2, type FROM gv$lock WHERE request>0)
ORDER BY id1, request;

Objects that have been lock for 2 minutes or more

SELECT SUBSTR(TO_CHAR(w.session_id),1,5) WSID, p1.spid WPID,
SUBSTR(s1.username,1,12) "WAITING User",
SUBSTR(s1.osuser,1,8) "OS User",
SUBSTR(s1.program,1,20) "WAITING Program",
s1.client_info "WAITING Client",
SUBSTR(TO_CHAR(h.session_id),1,5) HSID, p2.spid HPID,
SUBSTR(s2.username,1,12) "HOLDING User",
SUBSTR(s2.osuser,1,8) "OS User",
SUBSTR(s2.program,1,20) "HOLDING Program",
s2.client_info "HOLDING Client",
o.object_name "HOLDING Object"
FROM gv$process p1, gv$process p2, gv$session s1,
gv$session s2, dba_locks w, dba_locks h, dba_objects o
WHERE w.last_convert > 120
AND h.mode_held != 'None'
AND h.mode_held != 'Null'
AND w.mode_requested != 'None'
AND s1.row_wait_obj# = o.object_id
AND w.lock_type(+) = h.lock_type
AND w.lock_id1(+) = h.lock_id1
AND w.lock_id2 (+) = h.lock_id2
AND w.session_id = s1.sid (+)
AND h.session_id = s2.sid (+)
AND s1.paddr = p1.addr (+)
AND s2.paddr = p2.addr (+)
ORDER BY w.last_convert desc;

Creation date : 18/09/2008 @ 08:08
Last update : 18/09/2008 @ 08:08
Category : Oracle.Locks
Page read 662 times

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