Oracle Detect and Resolve Deadlocks.sqls

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Detect and Resolve LocksDetect and Resolve LocksAlso see How to debug PL/SQL code

How Oracle handle locking?

For managing access to shared resources oracle use enqueues as locking mechanism. Each enqueue represent a sharable resource. A shared resource can be a table definition, a transaction or any type of structure that represent something sharable between sessions. Each type of actions performed by Oracle sessions on thoseshared resources will require a certain type of lock or lock mode.

Each resource is represented by an enqueue. An enqueue is uniquely defined by itsTYPE, ID1 and ID2 (which are columns in the V$LOCK view). The name has the form: . Type has two characters and represent a resource type (e.g. TM for the table ition type). ID1 and ID2 are positive numbers and identify the resource fully (e.g. ID1 is the object_id of the table if the resource type is TM). For example canthere only be one enqueue for user SCOTTs EMP table (identified by TYPE=TM, ID1=object ID, ID2=0).

The most commonly known resource types are the TM, TX, ST and UL resources.

The TM resource, known as the DML enqueue, is acquired during the execution of a

statement when referencing a table so that the table is not dropped or alteredduring the execution of it.

The TX resource, known as the transaction enqueue, is acquired exclusive when atransaction initiates its first change and is held until the transaction does aCOMMIT or ROLLBACK. Row locking is based on TX enqueues. SMON will acquire it when doing recovery of a killed/crashed process.

The ST resource is used to serialize space management tasks when a sessions job requires extents to be allocated to objects.

The UL resource represent the user-defined locks defined by the DBMS_LOCK package.

The action select on a table will require that the executing session has a sharedlock on the resource table definition of the selected table so that other users should not change the table definition. When conflicting actions are occuring, Oracle will serialize the processing by putting a number of sessions in waiting mode until the work of the blocking session has been completed.

Acquiring a lock is the process of getting a lock on a resource on which we currently do not have a lock. Releasing locks are performed by the sessions when they issue a commit or a DDL statement (i.e. implicit commit), or by SMON if the sessions have been killed.

Row locking in Oracle is based on the TX enqueues and is known as transactional

locking. When two or more sessions are changing data on one row of a table (DMLstatements on the same record), the first session will lock the row by putting his transaction reference in the block containing the row header. The other sessions will look at this lock information and will wait on the transaction (i.e. the TX enqueue of the blocking session) of the first session before proceeding. When the first session performs a commit, the TX resource will be released and thewaiters will start their own locking. The waiting sessions are thus waiting onan exclusive TX resource, but their TM resources they are holding give the objects they are in fact waiting on.


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If a lock has not been acquired or converted, a deadlock check is made by the waiting session after a timeout.For example, following situation generates a deadlock:

user A gets an S lock on resource 1, then user B gets an S lock on resource 2;

later, A request an X lock on resource 2 and waits,then B requests an X lock onresource 1 and waits;

now, A is waiting for B to release resource 2, which is waiting for A to releaseresource 1;

A is indirectly waiting for A.It is a deadlock, generating a tracefile in the user_dump_dest and ORA-00060 inthe detecting session.

If a session holds an enqueue in share mode, other sessions can then alsotake the enqueue in share mode (for the same resource).

If a session holds an enqueue in exclusive mode, other sessions that wantsto get it - independently in which level - they have to wait.

The lock and resource information stands within the SGA to allow PMON torecover in the event of process failure. The PMON is responsible for

releasing the locks of the crashed/killed processes.

Common types of enqueues

JQ - Job Queue. When a job (submitted by DBMS_JOB.SUBMIT) is running, it isprotected by a JQ enqueue (which means that only one SNP-process can run the job).

ST - Space management Transaction. The ST enqueue is need to be held when the session isallocating/deallocating extents. If the session gets a timeout when requesting the

ST enqueue, "ORA-1575 timeout waiting for space management" is returned.

TM - DML (Table) enqueue - when a session wants to lock a table, a TM enqueue isrequested.

If a session deletes a row in the parent-table (DEPT) and a referential constraint

(foreign key) is created without an index on the child-table (EMP), or if the session

is updating the column(s) that the foreign key references to then a sharelock (level 4)

is taken on the child table. If another session tries to do changes to thechild-table

they have to wait (because they want the enqueue in row exclusive mode, and

that is notcompatible with the share mode). If an index is created on the child-table?

s foreign key-columnthen no share-lock is required on the child-table.

TX - Transaction. As soon as a transaction is started a TX enqueue is needed. Atransaction isuniquely defined by the rollback segment number.A session can be waiting on a TX enqueue for several reasons:


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27 enqueue releases 4 204 shows how many times an enqueue was released (freed).

The following query retrieves the event and the segment that caused the wait

Access Privileges: SELECT on dba_extents , v$session_wait

select username, event,segment_name, segment_typefrom dba_extents a, v$session_wait bwhereb.sid=74 anda.file_id = b.p1 andb.p2 between (a.block_id and a.block_id+a.blocks 1);The following locking information script provides informationregarding the locks currently held in the database.

Access Privileges: SELECT on V_$LOCK, V_$SESSION, SYS.USER$, SYS.OBJ$

selectnvl(S.USERNAME,'Internal') username,

L.SID,nvl(S.TERMINAL,'None') terminal,decode(command,

0,'None',decode(l.id2,0,U1.NAME||'.'||substr(T1.NAME,1,20),'None')) tab,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',


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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||' - ???') COMMAND,

decode(L.LMODE,1,'No Lock',2,'Row Share',


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3,'Row Exclusive',4,'Share',5,'Share Row Exclusive',6,'Exclusive','NONE') lmode,

decode(L.REQUEST,1,'No Lock',2,'Row Share',3,'Row Exclusive',4,'Share',5,'Share Row Exclusive',6,'Exclusive','NONE') request,

l.id1||'-'||l.id2 Laddr,l.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','MB','Master buffer hash table instance lock','MM','Mount definition gloabal enqueue lock','MR','Media recovery lock','PF','Password file lock','PI','Parallel operation lock',

'PR','Process startup lock','PS','Parallel operation lock','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','TT','Temporary table enqueue lock','TX','Transaction enqueue lock','UL','User supplied lock','UN','User name lock','US','Undo segment DDL lock',


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'WL','Being-written redo log instance lock','WS','Write-atomic-log-switch global enqueue lock','TS',decode(l.id2,0,'Temporary segment enqueue lock (ID2=0)',

'New block allocation enqueue lock (ID2=1)'),'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','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)','PG','Library cache pin instance lock (G=namespace)','PH','Library cache pin instance lock (H=namespace)','PI','Library cache pin instance lock (I=namespace)','PJ','Library cache pin instance lock (J=namespace)','PL','Library cache pin instance lock (K=namespace)','PK','Library cache pin instance lock (L=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)','PS','Library cache pin instance lock (S=namespace)','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)','QL','Row cache instance lock (K=cache)','QK','Row cache instance lock (L=cache)','QM','Row cache instance lock (M=cache)',


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'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)','????') Locktfrom V$LOCK L,

V$SESSION S,SYS.USER$ U1,SYS.OBJ$ T1

where L.SID = S.SIDand T1.OBJ# = decode(L.ID2,0,L.ID1,1)and U1.USER# = T1.OWNER#and S.TYPE != 'BACKGROUND'order by 1,2,5/The following script can be used to report the session

and tables that are blocking other sessions

Access Privileges: SELECT on V$LOCK,V$SESSION,SYS.USER$,SYS.OBJ$

select nvl(S.USERNAME,'Internal') username,nvl(S.TERMINAL,'None') terminal,L.SID||','||S.SERIAL# Kill,U1.NAME||'.'||substr(T1.NAME,1,20) tab,decode(L.LMODE,1,'No Lock',

2,'Row Share',3,'Row Exclusive',4,'Share',5,'Share Row Exclusive',

6,'Exclusive',null) lmode,decode(L.REQUEST,1,'No Lock',2,'Row Share',3,'Row Exclusive',4,'Share',5,'Share Row Exclusive',6,'Exclusive',null) request

from V$LOCK L,V$SESSION S,SYS.USER$ U1,SYS.OBJ$ T1

where L.SID = S.SIDand T1.OBJ# = decode(L.ID2,0,L.ID1,L.ID2)

and U1.USER# = T1.OWNER#and S.TYPE != 'BACKGROUND'and S.sid in(select blocking_session from v$session where blocking_session is not null)order by 1,2,5/This script will report the SQL text and Object names related tolocks currently being held in the database.

Access Privileges: SELECT on v$session, v$sqlarea, v$lock, v$locked_object, db


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a_objects

Query 1-------

SELECT c.object_name|| ' in session '|| a.session_id|| ' is blocking '|| d.object_name|| ' in session '|| b.session_id

FROM v$locked_object a,v$locked_object b,dba_objects c,dba_objects d,(SELECT l1.SID sid1, ' IS BLOCKING ' BLOCK, l2.SID sid2

FROM v$lock l1, v$lock l2WHERE l1.BLOCK = 1

AND l2.request > 0AND l1.id1 = l2.id1AND l1.id2 = l2.id2) l

WHERE l.sid1 = a.session_idAND l.sid2 = b.session_id

AND a.object_id = c.object_idAND b.object_id = d.object_idAND c.object_id = d.object_id;

query 2-------SELECT NVL (c.sql_text, 'sid=' || a.SID)

|| ' IS BLOCKING '|| CHR (10)|| d.sql_text

FROM v$session a,v$session b,v$sqlarea c,

v$sqlarea d,(SELECT l1.SID sid1, ' IS BLOCKING ' BLOCK, l2.SID sid2FROM v$lock l1, v$lock l2

WHERE l1.BLOCK = 1AND l2.request > 0AND l1.id1 = l2.id1AND l1.id2 = l2.id2) l

WHERE l.sid1 = a.SIDAND l.sid2 = b.SIDAND a.sql_address = c.address(+)AND b.sql_address = d.address;

Query 3

-------SELECTcase when c.sql_text is not null then'SID='||a.sid||' Obj='||o3.object_name||' sql="'||c.sql_text||'" is blocking 'else 'SID='||a.sid||' Obj='||o3.object_name||' is blocking ' end ||case when d.sql_text is not null then'SID='||b.sid||' Obj='||o4.object_name||' sql="'||d.sql_text||'"'else 'SID='||a.sid||' Obj='||o4.object_name endFROMv$session a,


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v$session b,v$sqlarea c,v$sqlarea d,v$lock l1,v$lock l2,v$locked_object o1,v$locked_object o2,dba_objects o3,dba_objects o4WHEREl1.BLOCK = 1AND l2.request > 0AND l1.id1 = l2.id1AND l1.id2 = l2.id2and l1.sid = a.SIDAND l2.sid = b.SIDAND a.sql_address = c.address(+)AND b.sql_address = d.addressand l1.sid = o1.session_idAND l2.sid = o2.session_idAND o1.object_id = o3.object_idAND o2.object_id = o4.object_id/This script produces information about locks being held or waited on in the data

base.

Access Privileges: SELECT on DBA_OBJECTS, V$LOCK, V$SESSION

select B.SID, C.USERNAME, C.OSUSER, C.TERMINAL,DECODE(B.ID2, 0, A.OBJECT_NAME,

'Trans-'||to_char(B.ID1)) OBJECT_NAME,B.TYPE,

DECODE(B.LMODE,0,'--Waiting--',1,'Null',2,'Row Share',3,'Row Excl',

4,'Share',

5,'Sha Row Exc',6,'Exclusive','Other') "Lock Mode",

DECODE(B.REQUEST,0,' ',1,'Null',2,'Row Share',3,'Row Excl',4,'Share',5,'Sha Row Exc',6,'Exclusive','Other') "Req Mode"

from DBA_OBJECTS A, V$LOCK B, V$SESSION Cwhere A.OBJECT_ID(+) = B.ID1

and B.SID = C.SIDand C.USERNAME is not null

order by B.SID, B.ID2;This script generates a report of users waiting for locks.

Access Privileges: SELECT on v$session, v$lock

SELECT sn.username, m.sid, m.type,DECODE(m.lmode, 0, 'None',

1, 'Null',


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2, 'Row Share',3, 'Row Excl.',4, 'Share',5, 'S/Row Excl.',6, 'Exclusive',

lmode, ltrim(to_char(lmode,'990'))) lmode,DECODE(m.request,0, 'None',

1, 'Null',2, 'Row Share',3, 'Row Excl.',4, 'Share',5, 'S/Row Excl.',6, 'Exclusive',request, ltrim(to_char(m.request,

'990'))) request, m.id1, m.id2FROM v$session sn, v$lock mWHERE (sn.sid = m.sid AND m.request != 0)

OR (sn.sid = m.sidAND m.request = 0 AND lmode != 4AND (id1, id2) IN (SELECT s.id1, s.id2

FROM v$lock sWHERE request != 0

AND s.id1 = m.id1AND s.id2 = m.id2)

)ORDER BY id1, id2, m.request;The following script displays the objects that are being locked

Access Privileges: SELECT on v$locked_object, dba_objects, v$lock, v$session

SELECT DISTINCT object_name|| ' '|| locked_mode|| ' '|| ctime|| ' '|| c.SID

|| ' '|| serial#FROM v$locked_object a, dba_objects b, v$lock c, v$session d

WHERE a.object_id = b.object_idAND c.SID = a.session_idAND c.SID = d.SID;

To find the query for blocking session

Access Privileges: SELECT on v$session, v$sqlarea

SELECT 'sid='|| a.SID|| ' Wait Class='

|| a.wait_class|| ' Time='|| a.seconds_in_wait|| CHR (10)|| ' Query='|| b.sql_text

FROM v$session a, v$sqlarea bWHERE a.blocking_session IS NOT NULL AND a.sql_address = b.address

ORDER BY a.blocking_session/


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The following PL/SQL script can be used to display Locked sessions hierachially

Access Privileges: SELECT on v$session

set serveroutput ON

DECLARETYPE array_num_type IS TABLE OF PLS_INTEGER

INDEX BY BINARY_INTEGER;

v_session_id array_num_type;v_blocking1 array_num_type;v_blocking2 array_num_type;v_blocking3 array_num_type;v_blocking4 array_num_type;v_blocking5 array_num_type;v_deadlock array_num_type;sn1 PLS_INTEGER;sn2 PLS_INTEGER;sn3 PLS_INTEGER;sn4 PLS_INTEGER;sn5 PLS_INTEGER;sn6 PLS_INTEGER;is_dead_lock BOOLEAN;

str VARCHAR2 (1000);BEGINFOR cur1 IN (SELECT SID, blocking_session

FROM v$sessionWHERE blocking_session IS NOT NULL

ORDER BY logon_time)LOOP

v_session_id (cur1.blocking_session) := cur1.SID;v_blocking1 (cur1.SID) := cur1.blocking_session;

END LOOP;

sn1 := v_blocking1.FIRST;

WHILE (sn1 IS NOT NULL)LOOPsn2 := v_blocking1 (sn1);is_dead_lock := FALSE;

IF v_blocking1.EXISTS (sn2)THEN

sn3 := v_blocking1 (sn2);v_blocking2 (sn1) := sn3;

IF sn3 = sn1THEN

is_dead_lock := TRUE;

END IF;



IF sn4 = sn1 OR sn4 = sn2THEN

is_dead_lock := TRUE;


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END IF;



IF sn1 = sn5 OR sn2 = sn5 OR sn3 = sn5THEN

is_dead_lock := TRUE;END IF;



IF sn1 = sn6 OR sn2 = sn6 OR sn3 = sn6 OR sn4 = sn6THEN

is_dead_lock := TRUE;END IF;

END IF;END IF;

END IF;

END IF;

IF is_dead_lock = TRUETHEN

v_deadlock (sn1) := 1;ELSE

v_deadlock (sn1) := 0;END IF;

sn1 := v_blocking1.NEXT (sn1);END LOOP;

sn1 := v_blocking1.FIRST;

WHILE (sn1 IS NOT NULL)LOOP

IF v_deadlock (sn1) = 0THEN

str := sn1;ELSE

str := 'Deadlock ' || sn1;END IF;


str := str || ' -> ' || v_blocking1 (sn1);

END IF;


str := str || ' -> ' || v_blocking2 (sn1);END IF;


str := str || ' -> ' || v_blocking3 (sn1);


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END IF;





sn1 := v_blocking1.NEXT (sn1);DBMS_OUTPUT.put_line (str);

END LOOP;END;/Data Dictionary Views related to Locks

V$SESSION_WAIT When a session is waiting on a resource, it can be found waitingon the enqueue wait event,e.g. SELECT * FROM V$SESSION_WAIT WHERE EVENT = 'enqueue';- SID identifier of session holding the lock- P1, P2, P3 determine the resource when event = 'enqueue'

- SECONDS_IN_WAIT gives how long the wait did occurs

V$SESSION session information and row locking information- SID, SERIAL# identifier of the session- LOCKWAIT address of the lock waiting, otherwise null- ROW_WAIT_OBJ# object identified of the object we are waiting on(object_id of dba_objects)- ROW_WAIT_FILE#, ROW_WAIT_BLOCK#, ROW_WAIT_ROW# file_id , block_id androw location within block of the locked row

V$LOCK list of all the locks in the system- SID identifier of session holding the lock- TYPE, ID1 and ID2 determine the resource

- LMODE and REQUEST indicate which queue the session is waiting on, as follows:LMODE > 0, REQUEST = 0 ownerLMODE = 0, REQUEST > 0 acquirerLMODE > 0, REQUEST > 0 converter- CTIME time since current mode was converted (see Note 223146.1)- BLOCK are we blocking another lockBLOCK = 0 non blockingBLOCK = 1 blocking others

DBA_LOCK or DBA_LOCKS formatted view on V$LOCK (created via$ORACLE_HOME/rdbms/admin/catblock.sql)- SESSION_ID == SID in V$LOCK- LOCK_TYPE, LOCK_ID1, LOCK_ID2 formatted value of TYPE, ID1, ID2 from V$LOCK

- MODE_HELD and MODE_REQUESTED formatted value of LMODE and REQUEST from V$LOCK- LAST_CONVERT == CTIME of V$LOCK- BLOCKING_OTHERS formatted value of BLOCK from V$LOCK

V$TRANSACTION_ENQUEUE subset of V$LOCK for the blocking TX resources only(same description as for the V$LOCK view)

V$ENQUEUE_LOCK subset of V$LOCK for the system resources only andblocked TX resources only. (same description as for the V$LOCK view)


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DBA_DML_LOCKS subset of the V$LOCK for the DML (TM) locks only(created via $ORACLE_HOME/rdbms/admin/catblock.sql- same description as the DBA_LOCK view)

V$LOCKED_OBJECT same info as DBA_DML_LOCKS, but linked with therollback and session information- XIDUSN, XIDSLOT and XIDSQN rollback information to be linked with V$TRANSACTION- OBJECT_ID object being locked- SESSION_ID session id- ORACLE_USERNAME oracle user name- OS_USER_NAME OS user name- PROCESS OS process id- LOCKED_MODE lock mode

V$RESOURCE list of all the currently locked resources in the system.Each row can be associated with one or more rows in V$LOCK- TYPE, ID1 and ID2 determine the resource

DBA_DDL_LOCKS has a row for each DDL lock that is being held, andone row for each outstanding request for a DDL lock. It is subset of DBA_LOCKSsame description as the DBA_LOCK view

DBA_WAITERS view that retrieve information for each session waiting on a

lock (created via $ORACLE_HOME/rdbms/admin/catblock.sql)- WAITING_SESSION waiting session- HOLDING_SESSION holding session- LOCK_TYPE, LOCK_ID1, LOCK_ID2 resource locked- MODE_HELD lock type held- MODE_REQUESTED lock type requested

DBA_BLOCKERS view that gives the blocking sessions (created via $ORACLE_HOME/rdbms/admin/catblock.sql)-HOLDING_SESSION holding session

Oracle Detect and Resolve Deadlocks.sqls

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