V$LOCK

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 system type locks are listed in Table 8-1. Be aware that not all types of locks are documented. To find a complete list of locks for the current release, query the V$LOCK_TYPE data dictionary view, described on "V$LOCK_TYPE".
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.

Table 8-1 Values for the TYPE Column: System Types

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

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