Dynamic Performance (V$) Views, 96 of 238

V$LOCK

This view lists the locks currently held by the Oracle database server 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 in Table 3-1.
`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`	The lock is blocking another lock

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`	Data file 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 commit 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