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Oracle Enqueue Names

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.

See Also: Oracle9i Application Developer's Guide - Advanced Queuing for more information on enqueues "DBA_LOCK_INTERNAL" and "DBA_LOCK"

The Oracle enqueues are:

• BL, Buffer Cache Management
• CF, Controlfile Transaction
• CI, Cross-instance Call Invocation
• CU, Bind Enqueue
• DF, Datafile
• DL, Direct Loader Index Creation
• DM, Database Mount
• DR, Distributed Recovery
• DX, Distributed TX
• FS, File Set
• IN, Instance Number
• IR, Instance Recovery
• IS, Instance State
• IV, Library Cache Invalidation
• JQ, Job Queue
• KK, Redo Log "Kick"
• L[A-P], Library Cache Lock
• MR, Media Recovery
• N[A-Z], Library Cache Pin
• PF, Password File
• PI, Parallel Slaves
• PR, Process Startup
• PS, Parallel Slave Synchronization
• Q[A-Z], Row Cache
• RT, Redo Thread
• SC, System Commit Number
• SM, SMON
• SQ, Sequence Number Enqueue
• SR, Synchronized Replication
• SS, Sort Segment
• ST, Space Management Transaction
• SV, Sequence Number Value
• TA, Transaction Recovery
• TM, DML Enqueue
• TS, Temporary Segment (also TableSpace)
• TT, Temporary Table
• 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