Oracle Enqueue Names

Oracle Enqueue Names

Enqueue（排队锁）是Oracle数据库中用于协调多进程并发访问共享资源的锁机制。

This appendix lists Oracle enqueues. Enqueues are shared memory structures (locks) that serialize access to database resources. They can be associated with a session or transaction. Enqueue names are displayed in the LOCK_TYPE column of the DBA_LOCK and DBA_LOCK_INTERNAL data dictionary views.

A resource uniquely identifies an object that can be locked by different sessions within an instance (local resource) or between instances (global resource). Each session that tries to lock the resource will have an enqueue on the resource.

Note:

The names of enqueues and their definitions may change from release to release.

The Oracle enqueues are:

BL, Buffer Cache Management

BR, Backup/Restore

CF, Controlfile Transaction

CI, Cross-instance Call Invocation

CU, Bind Enqueue

DF, Datafile

DL, Direct Loader Index Creation

DM, Database Mount

DR, Distributed Recovery Process

DW, SecureFiles

DX, Distributed Transaction

FP, File Object

FS, File Set

HW, High-Water Lock

IN, Instance Number

IR, Instance Recovery

IS, Instance State

IV, Library Cache Invalidation

JI, Enqueue used during AJV snapshot refresh

JQ, Job Queue

KK, Redo Log "Kick"

KP, contention in Oracle Data Pump startup and shutdown processes

KO, Multiple Object Checkpoint

L[A-P], Library Cache Lock

LS, Log Start or Switch

MM, Mount Definition

MR, Media Recovery

N[A-Z], Library Cache Pin

PE, ALTER SYSTEM SET PARAMETER = VALUE

PF, Password File

PI, Parallel Slaves

PR, Process Startup

PS, Parallel Slave Synchronization

Q[A-Z], Row Cache

RO, Object Reuse

RT, Redo Thread

RW, Row Wait

SC, System Change Number

SM, SMON

SN, Sequence Number

SQ, Sequence Number Enqueue

SR, Synchronized Replication

SS, Sort Segment

ST, Space Management Transaction

SV, Sequence Number Value

TA, Transaction Recovery

TC, Thread Checkpoint

TE, Extend Table

TM, DML Enqueue

TO, Temporary Table Object Enqueue

TS, Temporary Segment (also TableSpace)

TT, Tablespace

TX, Transaction

UL, User-defined Locks

UN, User Name

US, Undo Segment, Serialization

WL, Being Written Redo Log

XA, Instance Attribute Lock

XI, Instance Registration Lock

ZA, Exclusive Lock When Moving Audit Table

Enqueue状态查看

-- 查看当前enqueue等待
SELECT * FROM v$enqueue_stat WHERE cum_wait_time > 0;

-- 详细enqueue持有/等待情况
SELECT 
  e.addr, e.kaddr, e.sid, 
  e.type, e.id1, e.id2, 
  e.lmode, e.request, e.ctime
FROM v$lock e
WHERE e.type IN ('TX','TM','ST','TT','US','SQ','BL','HW')
ORDER BY e.ctime DESC;

注：Oracle不同版本可能有所差异，19c新增了TA(Tablespace Alter)等新enqueue类型。