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Oracle® Database Reference
10g Release 1 (10.1)

Part Number B10755-01
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V$LOCK

This view 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 in Table 4-1.

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

Table 4-1 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 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 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