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
`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
`MR`	Media recovery