V$LOCK

Oracle 11gR1

V$LOCK lists the locks currently held by the Oracle Database and outstanding requests for a lock or latch.

Column	Datatype	Description
ADDR	RAW(4 | 8)	Address of lock state object
KADDR	RAW(4 | 8)	Address of lock
SID	NUMBER	Identifier for session holding or acquiring the lock
TYPE	VARCHAR2(2)	Type of user or system lock The locks on the user types are obtained by user applications. Any process that is blocking others is likely to be holding one of these locks. The user type locks are: TM - DML enqueue TX - Transaction enqueue UL - User supplied The locks on the system types are held for extremely short periods of time. The system type locks are listed below.
ID1	NUMBER	Lock identifier #1 (depends on type)
ID2	NUMBER	Lock identifier #2 (depends on type)
LMODE	NUMBER	Lock mode in which the session holds the lock: · 0 - none · 1 - null (NULL) · 2 - row-S (SS) · 3 - row-X (SX) · 4 - share (S) · 5 - S/Row-X (SSX) · 6 - exclusive (X)
REQUEST	NUMBER	Lock mode in which the process requests the lock: · 0 - none · 1 - null (NULL) · 2 - row-S (SS) · 3 - row-X (SX) · 4 - share (S) · 5 - S/Row-X (SSX) · 6 - exclusive (X)
CTIME	NUMBER	Time since current mode was granted
BLOCK	NUMBER	A value of either 0 or 1, depending on whether or not the lock in question is the blocker.

Values for the TYPE Column: System Types

System Type	Description	System Type	Description
BL	Buffer hash table instance	NA..NZ	Library cache pin instance (A..Z = namespace)
CF	Control file schema global enqueue	PF	Password File
CI	Cross-instance function invocation instance	PI, PS	Parallel operation
CU	Cursor bind	PR	Process startup
DF	datafile instance	QA..QZ	Row cache instance (A..Z = cache)
DL	Direct loader parallel index create	RT	Redo thread global enqueue
DM	Mount/startup db primary/secondary instance	SC	System change number instance
DR	Distributed recovery process	SM	SMON
DX	Distributed transaction entry	SN	Sequence number instance
FS	File set	SQ	Sequence number enqueue
HW	Space management operations on a specific segment	SS	Sort segment
IN	Instance number	ST	Space transaction enqueue
IR	Instance recovery serialization global enqueue	SV	Sequence number value
IS	Instance state	TA	Generic enqueue
IV	Library cache invalidation instance	TS	Temporary segment enqueue (ID2=0)
JQ	Job queue	TS	New block allocation enqueue (ID2=1)
KK	Thread kick	TT	Temporary table enqueue
LA .. LP	Library cache lock instance lock (A..P = namespace)	UN	User name
MM	Mount definition global enqueue	US	Undo segment DDL
MR	Media recovery	WL	Being-written redo log instance

Note:

1. 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;

2. Show locked objects

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;

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