|
Enqueue
|
Enqueue Type
|
Description
|
|
Auto BMR
|
enq: AB - ABMR process initialized
|
Lock held to ensure that ABMR process is initialized
|
|
Auto BMR
|
enq: AB - ABMR process start/stop
|
Lock held to ensure that only one ABMR is started in
the cluster
|
|
ASM Disk AU Lock
|
enq: AD - allocate AU
|
Synchronizes accesses to a specific ASM disk AU
|
|
ASM Disk AU Lock
|
enq: AD - deallocate AU
|
Synchronizes accesses to a specific ASM disk AU
|
|
ASM Disk AU Lock
|
enq: AD - relocate AU
|
Synchronizes accesses to a specific ASM disk AU
|
|
Edition Lock
|
enq: AE - lock
|
Prevent Dropping an edition in use
|
|
Advisor Framework
|
enq: AF - task serialization
|
This enqueue is used to serialize access to an
advisor task
|
|
Analytic Workspace Generation
|
enq: AG - contention
|
Synchronizes generation use of a particular
workspace
|
|
ASM Enqueue
|
enq: AM - ASM ACD Relocation
|
Block ASM cache freeze
|
|
ASM Enqueue
|
enq: AM - ASM Amdu Dump
|
Allow only one AMDU dump when block read failure
|
|
ASM Enqueue
|
enq: AM - ASM File Destroy
|
Prevent same file deletion race
|
|
ASM Enqueue
|
enq: AM - ASM Grow ACD
|
Serializes growing ASM ACD
|
|
ASM Enqueue
|
enq: AM - ASM Password File Update
|
Allow one ASM password file update per cluster at a
time
|
|
ASM Enqueue
|
enq: AM - ASM User
|
Prevents a user from being dropped if it owns any
open files
|
|
ASM Enqueue
|
enq: AM - ASM cache freeze
|
Start ASM cache freeze
|
|
ASM Enqueue
|
enq: AM - ASM disk based alloc/dealloc
|
Synchronizes disk based allocations/deallocations
|
|
ASM Enqueue
|
enq: AM - ASM file descriptor
|
Serializes access to ASM file descriptors
|
|
ASM Enqueue
|
enq: AM - ASM file relocation
|
Serializes file relocation shrink and drop
|
|
ASM Enqueue
|
enq: AM - ASM reserved
|
Check id1 of call for specific purpose
|
|
ASM Enqueue
|
enq: AM - background COD reservation
|
Reserve a background COD entry
|
|
ASM Enqueue
|
enq: AM - block repair
|
Serializes block repairs
|
|
ASM Enqueue
|
enq: AM - client registration
|
Registers DB instance to ASM client state object
hash
|
|
ASM Enqueue
|
enq: AM - disk offline
|
Synchronizes disk offlines
|
|
ASM Enqueue
|
enq: AM - group block
|
ASM group block
|
|
ASM Enqueue
|
enq: AM - group use
|
Client group use
|
|
ASM Enqueue
|
enq: AM - rollback COD reservation
|
Reserve a rollback COD entry
|
|
ASM Enqueue
|
enq: AM - shutdown
|
Prevent DB instance registration during ASM instance
shutdown
|
|
MultiWriter Object Access
|
enq: AO - contention
|
Synchornizes access to objects and scalar variables
|
|
SPM Autopurge
|
enq: AP - contention
|
This enqueue is used to serialize the purging of SQL
plan baselines
|
|
Service Operations
|
enq: AS - service activation
|
Synchronizes new service activation
|
|
Alter Tablespace
|
enq: AT - contention
|
Serializes 'alter tablespace' operations
|
|
ASM volume locks
|
enq: AV - AVD client registration
|
Serialize inst reg and first DG use
|
|
ASM volume locks
|
enq: AV - add/enable first volume in DG
|
Serialize taking the AVD DG enqueue
|
|
ASM volume locks
|
enq: AV - persistent DG number
|
prevent DG number collisions
|
|
ASM volume locks
|
enq: AV - volume relocate
|
Serialize relocating volume extents
|
|
Analytic Workspace
|
enq: AW - AW generation lock
|
In-use generation state for a particular workspace
|
|
Analytic Workspace
|
enq: AW - AW state lock
|
Row lock synchronization for the AW$ table
|
|
Analytic Workspace
|
enq: AW - AW$ table lock
|
Global access synchronization to the AW$ table
|
|
Analytic Workspace
|
enq: AW - user access for AW
|
Synchronizes user accesses to a particular workspace
|
|
KSXA Test Affinity Dictionary
|
enq: AY - contention
|
Affinity Dictionary test affinity synchronization
|
|
Global Transaction Branch
|
enq: BB - 2PC across RAC instances
|
2PC distributed transaction branch across RAC
instances
|
|
BLOOM FILTER
|
enq: BF - PMON Join Filter cleanup
|
PMON bloom filter recovery
|
|
BLOOM FILTER
|
enq: BF - allocation contention
|
Allocate a bloom filter in a parallel statement
|
|
clonedb bitmap file access
|
enq: BM - clonedb bitmap file write
|
synchronizes clonedb bitmap file operations
|
|
Backup/Restore
|
enq: BR - file shrink
|
Lock held to prevent file from decreasing in
physical size during RMAN backup
|
|
Backup/Restore
|
enq: BR - multi-section restore header
|
Lock held to serialize file header access during
multi-section restore
|
|
Backup/Restore
|
enq: BR - multi-section restore section
|
Lock held to serialize section access during
multi-section restore
|
|
Backup/Restore
|
enq: BR - perform autobackup
|
Lock held to perform a new controlfile autobackup
|
|
Backup/Restore
|
enq: BR - proxy-copy
|
Lock held to allow cleanup from backup mode during
an RMAN proxy-copy backup
|
|
Backup/Restore
|
enq: BR - request autobackup
|
Lock held to request controlfile autobackups
|
|
Backup/Restore
|
enq: BR - space info datafile hdr update
|
Lock held to prevent multiple process to update the
headers at the same time
|
|
Calibration
|
enq: CA - contention
|
Synchronizes various IO calibration runs
|
|
Controlfile Transaction
|
enq: CF - contention
|
Synchronizes accesses to the controlfile
|
|
Cross-Instance Call Invocation
|
enq: CI - contention
|
Coordinates cross-instance function invocations
|
|
Label Security cache
|
enq: CL - compare labels
|
Synchronizes accesses to label cache for label
comparison
|
|
Label Security cache
|
enq: CL - drop label
|
Synchronizes accesses to label cache when dropping a
label
|
|
ASM Instance Enqueue
|
enq: CM - diskgroup dismount
|
serialize asm diskgroup dismount
|
|
ASM Instance Enqueue
|
enq: CM - gate
|
serialize access to instance enqueue
|
|
ASM Instance Enqueue
|
enq: CM - instance
|
indicate ASM diskgroup is mounted
|
|
KTCN REG enq
|
enq: CN - race with init
|
during descriptor initialization
|
|
KTCN REG enq
|
enq: CN - race with reg
|
during transaction commit to see concurrent
registrations
|
|
KTCN REG enq
|
enq: CN - race with txn
|
during registration
|
|
KTUCLO Master Slave enq
|
enq: CO - master slave det
|
enqueue held be Master in Cleanout Optim
|
|
Cleanup querycache registrations
|
enq: CQ - contention
|
Serializes access to cleanup client query cache
registrations
|
|
Reuse Block Range
|
enq: CR - block range reuse ckpt
|
Coordinates fast block range reuse ckpt
|
|
Block Change Tracking
|
enq: CT - CTWR process start/stop
|
Lock held to ensure that only one CTWR process is
started in a single instance
|
|
Block Change Tracking
|
enq: CT - change stream ownership
|
Lock held by one instance while change tracking is
enabled, to guarantee access
to
thread-specific resources
|
|
Block Change Tracking
|
enq: CT - global space management
|
Lock held during change tracking space management
operations that affect the
entire change
tracking file
|
|
Block Change Tracking
|
enq: CT - local space management
|
Lock held during change tracking space management
operations that affect
just the data for one thread
|
|
Block Change Tracking
|
enq: CT - reading
|
Lock held to ensure that change tracking data
remains in existence until a
reader is done with it
|
|
Block Change Tracking
|
enq: CT - state
|
Lock held while enabling or disabling change
tracking, to ensure that it is only
enabled or
disabled by one user at a time
|
|
Block Change Tracking
|
enq: CT - state change gate 1
|
Lock held while enabling or disabling change
tracking in RAC
|
|
Block Change Tracking
|
enq: CT - state change gate 2
|
Lock held while enabling or disabling change
tracking in RAC
|
|
Cursor
|
enq: CU - contention
|
Recovers cursors in case of death while compiling
|
|
TEXT: Index Specific Lock
|
enq: CX - TEXT: Index Specific Lock
|
Index Specific Lock on CTX index
|
|
DbsDriver
|
enq: DB - contention
|
Synchronizes modification of database wide
supplementallogging attributes
|
|
ASM Local Disk Group
|
enq: DD - contention
|
Synchronizes local accesses to ASM disk groups
|
|
Datafile Online in RAC
|
enq: DF - contention
|
Enqueue held by foreground or DBWR when a datafile
is brought online in RAC
|
|
ASM Disk Group Modification
|
enq: DG - contention
|
Synchronizes accesses to ASM disk groups
|
|
Direct Loader Index Creation
|
enq: DL - contention
|
Lock to prevent index DDL during direct load
|
|
Database Mount/Open
|
enq: DM - contention
|
Enqueue held by foreground or DBWR to syncrhonize
database mount/open
with other operations
|
|
Diskgroup number generator
|
enq: DN - contention
|
Serializes group number generations
|
|
ASM Disk Online Lock
|
enq: DO - Staleness Registry create
|
Synchronizes Staleness Registry creation
|
|
ASM Disk Online Lock
|
enq: DO - disk online
|
Synchronizes disk onlines and their recovery
|
|
ASM Disk Online Lock
|
enq: DO - disk online operation
|
Represents an active disk online operation
|
|
ASM Disk Online Lock
|
enq: DO - disk online recovery
|
Synchronizes disk onlines and their recovery
|
|
ASM Disk Online Lock
|
enq: DO - startup of MARK process
|
Synchronizes startup of MARK process
|
|
LDAP Parameter
|
enq: DP - contention
|
Synchronizes access to LDAP parameters
|
|
Distributed Recovery
|
enq: DR - contention
|
Serializes the active distributed recovery operation
|
|
Database Suspend
|
enq: DS - contention
|
Prevents a database suspend during LMON
reconfiguration
|
|
Default Temporary Tablespace
|
enq: DT - contention
|
Serializes changing the default temporary table
spaceand user creation
|
|
Diana Versioning
|
enq: DV - contention
|
Synchronizes access to lower-version Diana (PL/SQL
intermediate representation)
|
|
In memory Dispenser
|
enq: DW - contention
|
Serialize in memory dispenser operations
|
|
Distributed Transaction
|
enq: DX - contention
|
Serializes tightly coupled distributed transaction
branches
|
|
ASM File Access Lock
|
enq: FA - access file
|
Synchronizes accesses to open ASM files
|
|
Format Block
|
enq: FB - contention
|
Ensures that only one process can format data blcoks
in auto segment space
managed tablespaces
|
|
Disk Group Chunk Mount
|
enq: FC - open an ACD thread
|
LGWR opens an ACD thread
|
|
Disk Group Chunk Mount
|
enq: FC - recover an ACD thread
|
SMON recovers an ACD thread
|
|
Flashback Database
|
enq: FD - Flashback coordinator
|
Synchronization
|
|
Flashback Database
|
enq: FD - Flashback logical operations
|
Synchronization
|
|
Flashback Database
|
enq: FD - Flashback on/off
|
Synchronization
|
|
Flashback Database
|
enq: FD - Marker generation
|
Synchronization
|
|
Flashback Database
|
enq: FD - Restore point create/drop
|
Synchronization
|
|
Flashback Database
|
enq: FD - Tablespace flashback on/off
|
Synchronization
|
|
KTFA Recovery
|
enq: FE - contention
|
Serializes flashback archive recovery
|
|
ACD Relocation Gate Enqueue
|
enq: FG - FG redo generation enq race
|
resolve race condition to acquire Disk Group Redo
Generation Enqueue
|
|
ACD Relocation Gate Enqueue
|
enq: FG - LGWR redo generation enq race
|
resolve race condition to acquire Disk Group Redo
Generation Enqueue
|
|
ACD Relocation Gate Enqueue
|
enq: FG - serialize ACD relocate
|
only 1 process in the cluster may do ACD relocation
in a disk group
|
|
Flashback database log
|
enq: FL - Flashback database log
|
Synchronization
|
|
Flashback database log
|
enq: FL - Flashback db command
|
Enqueue used to synchronize Flashback Database and
and deletion of flashback logs.
|
|
File Mapping
|
enq: FM - contention
|
Synchronizes access to global file mapping state
|
|
File Object
|
enq: FP - global fob contention
|
Synchronizes various File Object(FOB) operations
|
|
Disk Group Recovery
|
enq: FR - contention
|
begin recovery of disk group
|
|
Disk Group Recovery
|
enq: FR - recover the thread
|
wait for lock domain detach
|
|
Disk Group Recovery
|
enq: FR - use the thread
|
indicate this ACD thread is alive
|
|
File Set / Dictionary Check
|
enq: FS - contention
|
Enqueue used to synchronize recovery and file
operations or synchronize dictionary check
|
|
Disk Group Redo Generation
|
enq: FT - allow LGWR writes
|
allow LGWR to generate redo in this thread
|
|
Disk Group Redo Generation
|
enq: FT - disable LGWR writes
|
prevent LGWR from generating redo in this thread
|
|
DBFUS
|
enq: FU - contention
|
This enqueue is used to serialize the capture of the
DB Feature Usage and High
Water Mark Statistics
|
|
ACD Xtnt Info CIC
|
enq: FX - issue ACD Xtnt Relocation CIC
|
ARB relocates ACD extent
|
|
ASM Disk Header
|
enq: HD - contention
|
Serializes accesses to ASM SGA data structures
|
|
Queue Page
|
enq: HP - contention
|
Synchronizes accesses to queue pages
|
|
Hash Queue
|
enq: HQ - contention
|
Synchronizes the creation of new queue IDs
|
|
Direct Loader High Water Mark
|
enq: HV - contention
|
Lock used to broker the high water mark during
parallel inserts
|
|
Segment High Water Mark
|
enq: HW - contention
|
Lock used to broker the high water mark during
parallel inserts
|
|
Internal
|
enq: IA - contention
|
|
|
NID
|
enq: ID - contention
|
Lock held to prevent other processes from performing
controlfile transaction while NID is running
|
|
Label Security
|
enq: IL - contention
|
Synchronizes accesses to internal label data
structures
|
|
Kti blr lock
|
enq: IM - contention for blr
|
Serializes block recovery for IMU txn
|
|
Instance Recovery
|
enq: IR - contention
|
Synchronizes instance recovery
|
|
Instance Recovery
|
enq: IR - contention2
|
Synchronizes parallel instance recovery and shutdown
immediate
|
|
Instance State
|
enq: IS - contention
|
Enqueue used to synchronize instance state changes
|
|
In-Mem Temp Table Meta Creation
|
enq: IT - contention
|
Synchronizes accesses to a temp object's metadata
|
|
Job Queue Date
|
enq: JD - contention
|
Synchronizes dates between job queue coordinator and
slave processes
|
|
Materialized View
|
enq: JI - contention
|
Lock held during materialized view operations (like
refresh, alter) to prevent concurrent operations on the same materialized
view
|
|
Job Queue
|
enq: JQ - contention
|
Lock to prevent multiple instances from running a
single job
|
|
Job Scheduler
|
enq: JS - aq sync
|
Scheduler evt code and AQ sync
|
|
Job Scheduler
|
enq: JS - contention
|
Synchronizes accesses to the job cache
|
|
Job Scheduler
|
enq: JS - evt notify
|
Lock got during event notification
|
|
Job Scheduler
|
enq: JS - evtsub add
|
Lock got when adding subscriber to event q
|
|
Job Scheduler
|
enq: JS - evtsub drop
|
Lock got when dropping subscriber to event q
|
|
Job Scheduler
|
enq: JS - job recov lock
|
Lock to recover jobs running on crashed RAC inst
|
|
Job Scheduler
|
enq: JS - job run lock - synchronize
|
Lock to prevent job from running elsewhere
|
|
Job Scheduler
|
enq: JS - q mem clnup lck
|
Lock obtained when cleaning up q memory
|
|
Job Scheduler
|
enq: JS - queue lock
|
Lock on internal scheduler queue
|
|
Job Scheduler
|
enq: JS - sch locl enqs
|
Scheduler non-global enqueues
|
|
Job Scheduler
|
enq: JS - wdw op
|
Lock got when doing window open/close
|
|
SQL STATEMENT QUEUE
|
enq: JX - SQL statement queue
|
statement
|
|
SQL STATEMENT QUEUE
|
enq: JX - cleanup of
queue
|
release SQL statement resources
|
|
Scheduler Master DBRM
|
enq: KD - determine DBRM master
|
Determine DBRM master
|
|
Scheduler
|
enq: KM - contention
|
Synchronizes various Resource Manager operations
|
|
Multiple Object Checkpoint
|
enq: KO - fast object checkpoint
|
Coordinates fast object checkpoint
|
|
Kupp Process Startup
|
enq: KP - contention
|
Synchronizes kupp process startup
|
|
ASM Attributes Enque
|
enq: KQ - access ASM attribute
|
Synchronization of ASM cached attributes
|
|
Scheduler Plan
|
enq: KT - contention
|
Synchronizes accesses to the current Resource
Manager plan
|
|
Materialized View Log DDL
|
enq: MD - contention
|
Lock held during materialized view log DDL
statements
|
|
AQ Notification Mail Host
|
enq: MH - contention
|
Lock used for recovery when setting Mail Host for AQ
e-mail notifications
|
|
Master Key
|
enq: MK - contention
|
changing values in enc$
|
|
AQ Notification Mail Port
|
enq: ML - contention
|
Lock used for recovery when setting Mail Port for AQ
e-mail notifications
|
|
LogMiner
|
enq: MN - contention
|
Synchronizes updates to the LogMiner dictionary and
prevents multiple instances from preparing the same LogMiner session
|
|
MMON restricted session
|
enq: MO - contention
|
Serialize MMON operations for restricted sessions
|
|
Media Recovery
|
enq: MR - contention
|
Lock used to coordinate media recovery with other
uses of datafiles
|
|
Media Recovery
|
enq: MR - standby role transition
|
Lock used to disallow concurrent standby role
transition attempt
|
|
Materialized View Refresh Log
|
enq: MS - contention
|
Lock held during materialized view refresh to setup
MV log
|
|
Online Datafile Move
|
enq: MV - datafile move
|
Held during online datafile move operation or
cleanup
|
|
MWIN Schedule
|
enq: MW - contention
|
This enqueue is used to serialize the calibration of
the manageability schedules
with the Maintenance Window
|
|
ksz synch
|
enq: MX - sync storage server info
|
Lock held to generate a response to the storage
server information request when an instance is starting up
|
|
Outline Cache
|
enq: OC - contention
|
Synchronizes write accesses to the outline cache
|
|
Online DDLs
|
enq: OD - Serializing DDLs
|
Lock to prevent concurrent online DDLs
|
|
Outline Name
|
enq: OL - contention
|
Synchronizes accesses to a particular outline name
|
|
OLAPI Histories
|
enq: OQ - xsoq*histrecb
|
Synchronizes access to olapi history parameter CB
|
|
OLAPI Histories
|
enq: OQ - xsoqhiAlloc
|
Synchronizes access to olapi history allocation
|
|
OLAPI Histories
|
enq: OQ - xsoqhiClose
|
Synchronizes access to olapi history closing
|
|
OLAPI Histories
|
enq: OQ - xsoqhiFlush
|
Synchronizes access to olapi history flushing
|
|
OLAPI Histories
|
enq: OQ - xsoqhistrecb
|
Synchronizes access to olapi history globals
|
|
TEXT: Generic Lock
|
enq: OT - TEXT: Generic Lock
|
CTX Generic Locks
|
|
Encryption Wallet
|
enq: OW - initialization
|
initializing the wallet context
|
|
Encryption Wallet
|
enq: OW - termination
|
terminate the wallet context
|
|
Property Lock
|
enq: PD - contention
|
Prevents others from updating the same property
|
|
Parameter
|
enq: PE - contention
|
Synchronizes system parameter updates
|
|
Password File
|
enq: PF - contention
|
Synchronizes accesses to the password file
|
|
Global Parameter
|
enq: PG - contention
|
Synchronizes global system parameter updates
|
|
AQ Notification Proxy
|
enq: PH - contention
|
Lock used for recovery when setting Proxy for AQ
HTTP notifications
|
|
Remote PX Process Spawn Status
|
enq: PI - contention
|
Communicates remote Parallel Execution Server Process
creation status
|
|
Transportable Tablespace
|
enq: PL - contention
|
Coordinates plug-in operation of transportable
tablespaces
|
|
Process Startup
|
enq: PR - contention
|
Synchronizes process startup
|
|
PX Process Reservation
|
enq: PS - contention
|
Parallel Execution Server Process reservation and
synchronization
|
|
ASM Partnership and Status Table
|
enq: PT - contention
|
Synchronizes access to ASM PST metadata
|
|
KSV slave startup
|
enq: PV - syncshut
|
Synchronizes instance shutdown_slvstart
|
|
KSV slave startup
|
enq: PV - syncstart
|
Synchronizes slave start_shutdown
|
|
Buffer Cache PreWarm
|
enq: PW - flush prewarm buffers
|
Direct Load needs to flush prewarmed buffers if DBWR
0 holds enqueue
|
|
Buffer Cache PreWarm
|
enq: PW - perwarm status in dbw0
|
DBWR 0 holds enqueue indicating prewarmed buffers
present in cache
|
|
ASM Rollback Recovery
|
enq: RB - contention
|
Serializes ASM rollback recovery operations
|
|
Result Cache: Enqueue
|
enq: RC - Result Cache: Contention
|
Coordinates access to a result-set
|
|
RAC Load
|
enq: RD - RAC load
|
update RAC load info
|
|
Block Repair/Resilvering
|
enq: RE - block repair contention
|
Synchronize block repair/resilvering operations
|
|
Data Guard Broker
|
enq: RF - DG Broker Current File ID
|
Identifies which configuration metadata file is
current
|
|
Data Guard Broker
|
enq: RF - FSFO Observer Heartbeat
|
Captures recent Fast-Start Failover Observer
heartbeat information
|
|
Data Guard Broker
|
enq: RF - FSFO Primary Shutdown suspended
|
Records when FSFO Primary Shutdown is suspended
|
|
Data Guard Broker
|
enq: RF - RF - Database Automatic Disable
|
Means for detecting when database is being
automatically disabled
|
|
Data Guard Broker
|
enq: RF - atomicity
|
Ensures atomicity of log transport setup
|
|
Data Guard Broker
|
enq: RF - new AI
|
Synchronizes selection of the new apply instance
|
|
Data Guard Broker
|
enq: RF - synch: DG Broker metadata
|
Ensures r/w atomicity of DG configuration metadata
|
|
Data Guard Broker
|
enq: RF - synchronization: aifo master
|
Synchronizes apply instance failure detection and
failover operation
|
|
Data Guard Broker
|
enq: RF - synchronization: critical ai
|
Synchronizes critical apply instance among primary
instances
|
|
wallet_set_mkey
|
enq: RK - set key
|
wallet master key rekey
|
|
RAC Encryption Wallet Lock
|
enq: RL - RAC wallet lock
|
RAC wallet lock
|
|
Redo Log Nab Computation
|
enq: RN - contention
|
Coordinates nab computations of online logs during
recovery
|
|
Multiple Object Reuse
|
enq: RO - contention
|
Coordinates flushing of multiple objects
|
|
Multiple Object Reuse
|
enq: RO - fast object reuse
|
Coordinates fast object reuse
|
|
Resilver / Repair
|
enq: RP - contention
|
Enqueue held when resilvering is needed or when
datablock is repaired from mirror
|
|
Workload Capture and Replay
|
enq: RR - contention
|
Concurrent invocation of DBMS_WORKLOAD_* package API
|
|
Reclaimable Space
|
enq: RS - file delete
|
Lock held to prevent file from accessing during
space reclaimation
|
|
Reclaimable Space
|
enq: RS - persist alert level
|
Lock held to make alert level persistent
|
|
Reclaimable Space
|
enq: RS - prevent aging list update
|
Lock held to prevent aging list update
|
|
Reclaimable Space
|
enq: RS - prevent file delete
|
Lock held to prevent deleting file to reclaim space
|
|
Reclaimable Space
|
enq: RS - read alert level
|
Lock held to read alert level
|
|
Reclaimable Space
|
enq: RS - record reuse
|
Lock held to prevent file from accessing while
reusing circular record
|
|
Reclaimable Space
|
enq: RS - write alert level
|
Lock held to write alert level
|
|
Redo Thread
|
enq: RT - contention
|
Thread locks held by LGWR, DBW0, and RVWR to
indicate mounted or open status
|
|
Redo Thread
|
enq: RT - thread internal enable/disable
|
Thread locks held by CKPT to synchronize thread
enable and disable
|
|
Rolling Migration
|
enq: RU - contention
|
Serializes rolling migration operations
|
|
Rolling Migration
|
enq: RU - waiting
|
Results of rolling migration CIC
|
|
Materialized View Flags
|
enq: RW - MV metadata contention
|
Lock held by CREATE/ALTER/DROP materialized
viewwhile updating materialized view flags in detail tables
|
|
ASM Extent Relocation Lock
|
enq: RX - relocate extent
|
Synchronizes relocating ASM extents
|
|
ASM Extent Relocation Lock
|
enq: RX - unlock extent
|
Synchronizes unlocking ASM extents
|
|
LogicalStandby
|
enq: SB - logical standby metadata
|
Synchronizes Logical Standby metadata operations
|
|
LogicalStandby
|
enq: SB - table instantiation
|
Synchronizes table instantiation and EDS operations
|
|
Session Migration
|
enq: SE - contention
|
Synchronizes transparent session migration operations
|
|
AQ Notification Sender
|
enq: SF - contention
|
Lock used for recovery when setting Sender for AQ
e-mail notifications
|
|
Active Session History Flushing
|
enq: SH - contention
|
Should seldom see this contention as this Enqueue is
always acquired in no-wait mode
|
|
Streams Table Instantiation
|
enq: SI - contention
|
Prevents multiple streams tabel instantiations
|
|
KTSJ Slave Task Cancel
|
enq: SJ - Slave Task Cancel
|
Serializes cancelling task executed by slave process
|
|
Shrink Segment
|
enq: SK - contention
|
Serialize shrink of a segment
|
|
Serialize Lock request
|
enq: SL - escalate lock
|
sending lock escalate to LCK0
|
|
Serialize Lock request
|
enq: SL - get lock
|
sending lock req to LCK0
|
|
Serialize Lock request
|
enq: SL - get lock for undo
|
sending lock req for undo to LCK0
|
|
Shared Object
|
enq: SO - contention
|
Synchronizes access to Shared Object (PL/SQL Shared
Object Manager)
|
|
Spare Enqueue
|
enq: SP - contention 1
|
(1) due to one-off patch
|
|
Spare Enqueue
|
enq: SP - contention 2
|
(2) due to one-off patch
|
|
Spare Enqueue
|
enq: SP - contention 3
|
(3) due to one-off patch
|
|
Spare Enqueue
|
enq: SP - contention 4
|
(4) due to one-off patch
|
|
Sequence Cache
|
enq: SQ - contention
|
Lock to ensure that only one process can replenish
the sequence cache
|
|
Synchronized Replication
|
enq: SR - contention
|
Coordinates replication / streams operations
|
|
Sort Segment
|
enq: SS - contention
|
Ensures that sort segments created during parallel
DML operations aren't prematurely cleaned up
|
|
Space Transaction
|
enq: ST - contention
|
Synchronizes space management activities in
dictionary-managed tablespaces
|
|
SaveUndo Segment
|
enq: SU - contention
|
Serializes access to SaveUndo Segment
|
|
Suspend Writes
|
enq: SW - contention
|
Coordinates the 'alter system suspend' operation
|
|
Instance Undo
|
enq: TA - contention
|
Serializes operations on undo segments and undo
tablespaces
|
|
SQL Tuning Base Existence Cache
|
enq: TB - SQL Tuning Base Cache Load
|
Synchronizes writes to the SQL Tuning Base Existence
Cache
|
|
SQL Tuning Base Existence Cache
|
enq: TB - SQL Tuning Base Cache Update
|
Synchronizes writes to the SQL Tuning Base Existence
Cache
|
|
Tablespace Checkpoint
|
enq: TC - contention
|
Lock held to guarantee uniqueness of a tablespace
checkpoint
|
|
Tablespace Checkpoint
|
enq: TC - contention2
|
Lock of setup of a unqiue tablespace checkpoint in
null mode
|
|
KTF map table enqueue
|
enq: TD - KTF dump entries
|
KTF dumping time/scn mappings in SMON_SCN_TIME table
|
|
KTF broadcast
|
enq: TE - KTF broadcast
|
KTF broadcasting
|
|
Temporary File
|
enq: TF - contention
|
Serializes dropping of a temporary file
|
|
Threshold Chain
|
enq: TH - metric threshold evaluation
|
Serializes threshold in-memory chain access
|
|
Auto Task Serialization
|
enq: TK - Auto Task Serialization
|
Lock held by MMON to prevent other MMON spawning of
Autotask Slave
|
|
Auto Task Serialization
|
enq: TK - Auto Task Slave Lockout
|
Serializes spawned Autotask Slaves
|
|
Log Lock
|
enq: TL - contention
|
Serializes threshold log table read and update
|
|
DML
|
enq: TM - contention
|
Synchronizes accesses to an object
|
|
Temp Object
|
enq: TO - contention
|
Synchronizes DDL and DML operations on a temp object
|
|
Runtime Fixed Table Purge
|
enq: TP - contention
|
Lock held during purge and dynamic reconfiguration
of fixed tables.
|
|
Queue table enqueue
|
enq: TQ - DDL contention
|
TM access to the queue table
|
|
Queue table enqueue
|
enq: TQ - DDL-INI contention
|
Streams DDL on queue table
|
|
Queue table enqueue
|
enq: TQ - INI contention
|
TM access to the queue table
|
|
Queue table enqueue
|
enq: TQ - TM contention
|
TM access to the queue table
|
|
Temporary Segment
|
enq: TS - contention
|
Serializes accesses to temp segments
|
|
Tablespace
|
enq: TT - contention
|
Serializes DDL operations on tablespaces
|
|
Cross-Instance Transaction
|
enq: TW - contention
|
Lock held by one instance to wait for transactions
on all instances to finish
|
|
Transaction
|
enq: TX - allocate ITL entry
|
Allocating an ITL entry in order to begin a
transaction
|
|
Transaction
|
enq: TX - contention
|
Lock held by a transaction to allow other
transactions to wait for it
|
|
Transaction
|
enq: TX - index contention
|
Lock held on an index during a split to prevent
other operations on it
|
|
Transaction
|
enq: TX - row lock contention
|
Lock held on a particular row by a transaction to
prevent other transactions from modifying it
|
|
User-defined
|
enq: UL - contention
|
Lock used by user applications
|
|
Undo Segment
|
enq: US - contention
|
Lock held to perform DDL on the undo segment
|
|
AQ Notification Watermark
|
enq: WA - contention
|
Lock used for recovery when setting Watermark for
memory usage in AQ notifications
|
|
AWR Flush
|
enq: WF - contention
|
This enqueue is used to serialize the flushing of
snapshots
|
|
Write gather local enqueue
|
enq: WG - delete fso
|
acquire lobid local enqueue when deleting fso
|
|
Write gather local enqueue
|
enq: WG - lock fso
|
acquire lobid local enqueue when locking fso
|
|
Being Written Redo Log
|
enq: WL - RAC-wide SGA contention
|
Serialize access to RAC-wide SGA
|
|
Being Written Redo Log
|
enq: WL - RFS global state contention
|
Serialize access to RFS global state
|
|
Being Written Redo Log
|
enq: WL - Test access/locking
|
Testing redo transport access/locking
|
|
Being Written Redo Log
|
enq: WL - contention
|
Coordinates access to redo log files and archive
logs
|
|
WLM Plan Operations
|
enq: WM - WLM Plan activation
|
Synchronizes new WLM Plan activation
|
|
AWR Purge
|
enq: WP - contention
|
This enqueue handles concurrency between purging and
baselines
|
|
LNS archiving log
|
enq: WR - contention
|
Coordinates access to logs by Async LNS and ARCH/FG
|
|
XDB Configuration
|
enq: XC - XDB Configuration
|
Lock obtained when incrementing XDB configuration
version number
|
|
Auto Online Exadata disks
|
enq: XD - ASM disk OFFLINE
|
Serialize OFFLINE Exadata disk operations
|
|
Auto Online Exadata disks
|
enq: XD - ASM disk ONLINE
|
Serialize ONLINE Exadata disk operations
|
|
Auto Online Exadata disks
|
enq: XD - ASM disk drop/add
|
Serialize Auto Drop/Add Exadata disk operations
|
|
AQ Notification No-Proxy
|
enq: XH - contention
|
Lock used for recovery when setting No Proxy Domains
for AQ HTTP notifications
|
|
ASM Extent Fault Lock
|
enq: XL - fault extent map
|
Keep multiple processes from faulting in the same
extent chunk
|
|
ASM Extent Relocation Enqueue
|
enq: XQ - purification
|
wait for relocation before doing block purification
|
|
ASM Extent Relocation Enqueue
|
enq: XQ - recovery
|
prevent relocation during _recovery_asserts checking
|
|
ASM Extent Relocation Enqueue
|
enq: XQ - relocation
|
wait for recovery before doing relocation
|
|
Quiesce / Force Logging
|
enq: XR - database force logging
|
Lock held during database force logging mode
|
|
Quiesce / Force Logging
|
enq: XR - quiesce database
|
Lock held during database quiesce
|
|
Internal Test
|
enq: XY - contention
|
Lock used for internal testing
|
|
Audit Partition
|
enq: ZA - add std audit table partition
|
lock held to add partition to std audit table
|
|
FGA Partition
|
enq: ZF - add fga audit table partition
|
lock held to add partition to fga audit table
|
|
File Group
|
enq: ZG - contention
|
Coordinates file group operations
|
|
Compression Analyzer
|
enq: ZH - compression analysis
|
Synchronizes analysis and insert into compression$,
prevents multiple threads analyzing the same table during a load
|
|
Global Context Action
|
enq: ZZ - update hash tables
|
lock held for updating global context hash tables |