Oracle常见后台进程及其功能汇总
Name Expanded Name Short Description Long Description External Properties
ABMRAuto BMR Background ProcessCoordinates execution of tasks such as filteringduplicate block media recovery requests and performing flood controlWhen a process submits a block media recoveryrequest to ABMR, it dynamically spawns slave processes (BMRn) toperform the recovery. ABMR and BMRn terminate after being idlefor a long time.See Also: Oracle Database Backup and Recovery User's GuideDatabase instance
ACFSASM Cluster File System CSS ProcessTracks the cluster membership in CSS and informs thefile system driver of membership changesACFS delivers CSS membership changes to the Oraclecluster file system. These membership changes are required for the filesystem to maintain file system consistency within the cluster.ASM instance, Oracle RAC
ACMSAtomic Control File to Memory Service ProcessCoordinates consistent updates to a control fileresource with its SGA counterpart on all instances in an Oracle RACenvironmentThe ACMS process works with a coordinating caller toensure that an operation is executed on every instance in Oracle RAC despitefailures. ACMS is the process in which a distributed operation is called. Asa result, this process can exhibit a variety of behaviors. In general, ACMSis limited to small, nonblocking state changes for a limited set ofcross-instance operations.Database instance, Oracle RAC
APnnLogical Standby / Streams Apply Process CoordinatorProcessObtains transactions from the reader server andpasses them to apply serversThe coordinator process name is APnn,where nn can include letters and numbers.See Also: Oracle Streams Concepts and AdministrationDatabase instance, Data Guard, Oracle Streams
ARBnASM Rebalance ProcessRebalances data extents within an ASM disk groupPossible processes are ARB0-ARB9 and ARBA.ASM instance
ARCnArchiver ProcessCopies the redo log files to archival storage whenthey are full or an online redo log switch occursARCn processes exist only when thedatabase is in ARCHIVELOG modeand automatic archiving is enabled, in which case ARCn automaticallyarchives online redo log files. LGWR cannot reuse and overwrite an onlineredo log group until it has been archived.The database starts multiple archiver processes as needed to ensure thatthe archiving of filled online redo logs does not fall behind. Possibleprocesses include ARC0-ARC9 and ARCa-ARCt.The LOG_ARCHIVE_MAX_PROCESSES initializationparameter specifies the number of ARCn processes that thedatabase initially invokes.See Also: Oracle Database Concepts and Oracle Database Administrator's GuideDatabase instance
ASMBASM Background ProcessCommunicates with the ASM instance, managing storageand providing statisticsASMB runs in ASM instances when the ASMCMD cp command runs or when the database instance first starts if theserver parameter file is stored in ASM. ASMB also runs with Oracle ClusterRegistry on ASM.Database and ASM instances
ASnnLogical Standby / Streams Apply Process ReaderServer or Apply Server
[*]Computes dependencies between logical change records (LCRs) and assembles messages into transactions (Reader Server)
[*]Applies LCRs to database objects or passes LCRs and user messages to their appropriate apply handlers (Apply Server)
When the reader server finishes computingdependencies between LCRs and assembling transactions, it returns theassembled transactions to the coordinator process. Query V$STREAMS_APPLY_READER for information about the reader server backgroundprocess.An apply server receives the transactions from the coordinatorbackground process, and either applies database changes in LCRs or sends LCRsor messages to apply handlers. Apply servers can also enqueue a queue. If anapply server encounters an error, then it then tries to resolve the errorwith a user-specified conflict handler or error handler. If an apply servercannot resolve an error, then it rolls back the transaction and places theentire transaction, including all of its messages, in the error queue. Whenan apply server commits a completed transaction, this transaction has beenapplied. When an apply server places a transaction in the error queue andcommits, this transaction also has been applied. Query V$STREAMS_APPLY_SERVER for information about the apply server backgroundprocess.The coordinator process name is ASnn, where nn caninclude letters and numbers.Database instance
BMRnAutomatic Block Media Recovery Slave Pool ProcessFetches blocks from a real-time readable standbydatabaseWhen a process submits a block media recoveryrequest to ABMR, it dynamically spawns slave processes (BMRn) toperform the recovery. BMRn processes fetch blocks from areal-time readable standby database. ABMR and BMRn terminateafter being idle for a long time.See Also: Oracle Database Backup and Recovery User's GuideDatabase instance
BnnnASM Blocking Slave Process for GMONPerforms maintenance actions on ASM disk groupsBnnn performs actions that requirewaiting for resources on behalf of GMON. GMON must be highly available andcannot wait.A Bnnn slave is spawned when a disk is taken offline in anASM disk group. Offline timer processing and drop of the disk are performedin this slave. Up to five process (B000 to B004) can exist depending on theload.ASM instance
CJQ0Job Queue Coordinator ProcessSelects jobs that need to be run from the datadictionary and spawns job queue slave processes (Jnnn) to run the jobsCJQ0 is automatically started and stopped as neededby Oracle Scheduler.The JOB_QUEUE_PROCESSES initializationparameter specifies the maximum number of processes that can be created forthe execution of jobs. CJQ0 starts only as many job queue processes asrequired by the number of jobs to run and available resources.See Also: Oracle Database Concepts and Oracle Database Administrator's GuideDatabase instance
CKPTCheckpoint ProcessSignals DBWn at checkpoints and updatesall the data files and control files of the database to indicate the mostrecent checkpointAt specific times CKPT starts a checkpoint requestby messaging DBWnto begin writing dirty buffers. On completion ofindividual checkpoint requests, CKPT updates data file headers and controlfiles to record most recent checkpoint.See Also: Oracle Database ConceptsDatabase and ASM instances
CPnnStreams Capture ProcessCaptures database changes from the redo log by usingthe infrastructure of LogMinerThe capture process name is CPnn, where nn caninclude letters and numbers. The underlying LogMiner process name is MSnn,where nn can include letters and numbers. The captureprocess includes one reader server that reads the redo log and divides itinto regions, one or more preparer servers that scan the redo log, and onebuilder server that merges redo records from the preparer servers. Eachreader server, preparer server, and builder server is a process. Query theV$STREAMS_CAPTURE view for information about this backgroundprocess.See Also: Oracle Streams Concepts and AdministrationDatabase instance, Oracle Streams
CSnnStreams Propagation Sender ProcessSends LCRs to a propagation receiverThe propagation sender process name is CSnn,where nn can include letters and numbers. In an OracleStreams combined capture and apply optimization, the propagation sender sendsLCRs directly to the propagation receiver to improve performance. Thepropagation receiver passes the LCRs to an apply process. Query V$PROPAGATION_SENDER for information about a propagation sender.Database instance, Oracle Streams
CSnnI/O Calibration ProcessIssues I/Os to storage as part of storagecalibration.CSnn slave processes are started onexecution of theDBMS_RESOURCE_MANAGER.CALIBRATE_IO() procedure. There is one slave process per CPU on each node of thedatabase.Database instance, Oracle RAC
CTWRChange Tracking Writer ProcessTracks changed data blocks as part of the RecoveryManager block change tracking featureCTWR tracks changed blocks as redo is generated at aprimary database and as redo is applied at a standby database. The process isslightly different depending on the type of database.See Also: Oracle Database Backup and Recovery User's GuideDatabase instance
DBRMDatabase Resource Manager ProcessSets resource plans and performs other tasks relatedto the Database Resource ManagerIf a resource plan is not enabled, then this processis idle.See Also: Oracle Database Administrator's GuideDatabase instance
DBWnDatabase Writer ProcessWrites modified blocks from the database buffercache to the data filesThe primary responsibility of DBWn is towrite data blocks to disk. DBWnalso handles checkpoints, file opensynchronization, and logging of Block Written records.In many cases the blocks that DBWn writes are scatteredthroughout the disk. Thus, the writes tend to be slower than the sequentialwrites performed by LGWR. DBWn performs multiblock writes whenpossible to improve efficiency. The number of blocks written in a multiblockwrite varies by operating system.The DB_WRITER_PROCESSES initializationparameter specifies the number of DBWn processes (DBW0-DBW9 andDBWa-DBWz). The database selects an appropriate default setting for thisparameter or adjusts a user-specified setting based on the number of CPUs andprocessor groups.See Also: Oracle Database Concepts and Oracle Database Performance Tuning GuideDatabase instance
DIA0Diagnostic Process
Detects and resolves hangs and deadlocks ASM and Database instances
DIAGDiagnostic Capture Process
Performs diagnostic dumps
DIAG performs diagnostic dumps requested by other processes and dumpstriggered by process or instance termination. In Oracle RAC, DIAG performsglobal diagnostic dumps requested by remote instances.ASM and Database instances
DMnnData Pump Master ProcessCoordinates the Data Pump job tasks performed byData Pump worker processes and handles client interactionsThe Data Pump master (control) process is startedduring job creation and coordinates all tasks performed by the Data Pump job.It handles all client interactions and communication, establishes all jobcontexts, and coordinates all worker process activities on behalf of the job.Database instance, Data Pump
DMONData Guard Broker Monitor ProcessManages and monitors a database that is part of aData Guard broker configurationWhen you start the Data Guard broker, a DMON processis created. DMON runs for every database instance that is managed by thebroker. DMON interacts with the local database and the DMON processes of theother databases to perform the requested function. DMON also monitors thehealth of the broker configuration and ensures that every database has aconsistent description of the configuration.DMON maintains profiles about all database objects in the brokerconfiguration in a binary configuration file. A copy of this file ismaintained by the DMON process for each of the databases that belong to thebroker configuration. The process is created when theDG_BROKER_START initialization parameter is set to true.See Also: Oracle Data Guard BrokerDatabase instance, Data Guard
DnnnDispatcher ProcessPerforms network communication in the shared serverarchitectureIn the shared server architecture, clients connectto a dispatcher process, which creates a virtual circuit for each connection.When the client sends data to the server, the dispatcher receives the datainto the virtual circuit and places the active circuit on the common queue tobe picked up by an idle shared server. The shared server then reads the datafrom the virtual circuit and performs the database work necessary to completethe request. When the shared server must send data to the client, the serverwrites the data back into the virtual circuit and the dispatcher sends thedata to the client. After the shared server completes the client request, theserver releases the virtual circuit back to the dispatcher and is free tohandle other clients.Several initialization parameters relate to shared servers. Theprincipal parameters are: DISPATCHERS, SHARED_SERVERS, MAX_SHARED_SERVERS,LOCAL_LISTENER, REMOTE_LISTENER.See Also: Oracle Database ConceptsDatabase instance, shared servers
DRnnASM Disk Resynchronization Slave ProcessResynchronizes the contents of an offline diskWhen a disk online SQL command is issued on a diskor disks that are offline, ASM spawns DRnn. Depending on the load,more than one slave may be spawned.ASM Instance
DSKMSlave Diskmon ProcessActs as the conduit between the database, ASMinstances, and the Master Diskmon daemon to communicate information toExadata storageThis process is active only if Exadata Storage isused. DSKM performs operations related to Exadata I/O fencing and Exadatacell failure handling.ASM instance, Exadata
DWnnData Pump Worker ProcessPerforms Data Pump tasks as assigned by the DataPump master processThe Data Pump worker process is responsible forperforming tasks that are assigned by the Data Pump master process, such asthe loading and unloading of metadata and data.Database instance
EMNCEMON Coordinator ProcessCoordinates database event management andnotificationsEMNC coordinates event management and notificationactivity in the database, including Streams Event Notifications, ContinuousQuery Notifications, and Fast Application Notifications.Database and ASM instances
EnnnEMON Slave ProcessPerforms database event management and notificationsThe database event management and notification loadis distributed among the EMON slave processes. These processes work on thesystem notifications in parallel, offering a capability to process a largervolume of notifications, a faster response time, and a lower shared memoryuse for staging notifications.Database and ASM instances
FBDAFlashback Data Archiver ProcessArchives historical rows for tracked tables intoflashback data archives and manages archive space, organization, andretentionWhen a transaction that modifies a tracked tablecommits, FBDA stores the pre-image of the rows in the archive. FDBA maintainsmetadata on the current rows and tracks how much data has been archived.FBDA is also responsible for automatically managing the flashback dataarchive for space, organization (partitioning tablespaces), and retention.FBDA also keeps track of how far the archiving of tracked transactions hasprogressed.See Also: Oracle Database Advanced Application Developer's GuideDatabase and ASM instances
FMONFile Mapping Monitor ProcessManages mapping information for the Oracle Databasefile mapping interfaceThe DBMS_STORAGE_MAP package enables you to control the mapping operations. Wheninstructed by the user, FMON builds mapping information and stores it in theSGA, refreshes the information when a change occurs, saves the information tothe data dictionary, and restores it to the SGA at instance startup.FMON is started by the database whenever the FILE_MAPPING initialization parameter is set to true.Database and ASM instances
FSFPData Guard Broker Fast Start Failover Pinger ProcessMaintains fast-start failover state between theprimary and target standby databasesFSFP is created when fast-start failover is enabled.Database instance, Data Guard
GCRnFoot 1 Global Conflict Resolution Slave ProcessPerforms synchronous tasks on behalf of LMHBGCRn processes are transient slaves thatare started and stopped as required by LMHB to perform synchronous orresource intensive tasks.Database and ASM instances, Oracle RAC
GEN0General Task Execution ProcessPerforms required tasks including SQL and DML Database and ASM instances
GMONASM Disk Group Monitor ProcessMonitors all mounted ASM disk groupsGMON monitors all the disk groups mounted in an ASMinstance and is responsible for maintaining consistent disk membership andstatus information. Membership changes result from adding and dropping disks,whereas disk status changes result from taking disks offline or bringing themonline.ASM instance
GTXnGlobal Transaction ProcessProvides transparent support for XA globaltransactions in an Oracle RAC environmentThese processes help maintain the global informationabout XA global transactions throughout the cluster. Also, the processes helpperform two-phase commit for global transactions anywhere in the cluster sothat an Oracle RAC database behaves as a single system to the externallycoordinated distributed transactions.The GLOBAL_TXN_PROCESSES initializationparameter specifies the number of GTXn processes, where n is0-9 or a-j. The database automatically tunes the number of these processesbased on the workload of XA global transactions. You can disable theseprocesses by setting the parameter to 0. If you try to run XA globaltransactions with these process disabled, an error is returned.See Also: Oracle Real Application Clusters Administration andDeployment GuideDatabase instance, Oracle RAC
InnnDisk and Tape I/O Slave ProcessServes as an I/O slave process spawned on behalf ofDBWR, LGWR, or an RMAN backup sessionI/O slave process can be configured on platformswhere asynchronous I/O support is not available. These slaves are started bysetting the corresponding slave enable parameter in the server parameterfile. The I/O slaves simulate the asynchronous I/O behavior when theunderlying platform does not have native support for asynchronous I/O.Database instance
INSVData Guard Broker Instance Slave ProcessPerforms Data Guard broker communication amonginstances in an Oracle RAC environmentINSV is created when the DG_BROKER_START initialization parameter is set to true.Database instance, Data Guard
JnnnJob Queue Slave ProcessExecutes jobs assigned by the job coordinatorJob slave processes are created or awakened by thejob coordinator when it is time for a job to be executed.Job slaves gather all the metadata required to run the job from the datadictionary. The slave processes start a database session as the owner of thejob, execute triggers, and then execute the job. After the job is complete,the slave processes commit and then execute appropriate triggers and closethe session. The slave can repeat this operation in case additional jobs needto be run.Database instance
LCK0Instance Enqueue Background ProcessManages global enqueue requests and cross-instancebroadcastsThe process handles all requests for resources otherthan data blocks. For examples, LCK0 manages library and row cache requests.Database and ASM instances, Oracle RAC
LGWRLog Writer ProcessWrites redo entries to the online redo logRedo log entries are generated in the redo logbuffer of the system global area (SGA). LGWR writes the redo log entriessequentially into a redo log file. If the database has a multiplexed redolog, then LGWR writes the redo log entries to a group of redo log files.See Also: Oracle Database Concepts and Oracle Database Administrator's GuideDatabase and ASM instances
LMD0Global Enqueue Service Daemon 0 ProcessManages incoming remote resource requests from otherinstancesLMD0 processes enqueue resources managed underGlobal Enqueue Service. In particular, LMD0 processes incoming enqueuerequest messages and controls access to global enqueues. It also performsdistributed deadlock detections.Database and ASM instances, Oracle RAC
LMHBGlobal Cache/Enqueue Service Heartbeat MonitorMonitor the heartbeat of LMON, LMD, and LMSn processesLMHB monitors LMON, LMD, and LMSn processesto ensure they are running normally without blocking or spinning.Database and ASM instances, Oracle RAC
LMONGlobal Enqueue Service Monitor ProcessMonitors an Oracle RAC cluster to manage globalresourcesLMON maintains instance membership within OracleRAC. The process detects instance transitions and performs reconfiguration ofGES and GCS resources.See Also: Oracle Real Application Clusters Administration andDeployment GuideDatabase and ASM instances, Oracle RAC
LMSnGlobal Cache Service ProcessManages resources and provides resource controlamong Oracle RAC instancesLMS, where n is 0-9 or a-z,maintains a lock database for Global Cache Service (GCS) and buffer cacheresources. This process receives, processes, and sends GCS requests, blocktransfers, and other GCS-related messages.See Also: Oracle Real Application Clusters Administration andDeployment GuideDatabase and ASM instances, Oracle RAC
LSP0Logical Standby Coordinator ProcessSchedules transactions for Data Guard SQL ApplyLSP0 is the initial process created upon startup ofData Guard SQL Apply. In addition to managing LogMiner and Apply processes,LSP0 is responsible for maintaining inter-transaction dependencies andappropriately scheduling transactions with applier processes. LSP0 is alsoresponsible for detecting and enabling runtime parameter changes for the SQLApply product as a whole.Database instance, Data Guard
LSP1Logical Standby Dictionary Build ProcessPerforms a logical standby dictionary build on aprimary databaseThe LSP1 process is spawned on a logical standbydatabase that is intended to become the new primary database. A logicalstandby database becomes a primary database by means of switchover orfailover. The dictionary is necessary for logical standby databases tointerpret the redo of the new primary database.Database instance, Data Guard
LSP2Logical Standby Set Guard ProcessDetermines which database objects will be protectedby the database guardThe LSP2 process is created as needed during startupof SQL Apply to update the list of objects that are protected by the databaseguard.Database instance, Data Guard
LnnnPooled Server ProcessHandles client requests in Database ResidentConnection PoolingIn Database Resident Connection Pooling, clientsconnect to a connection broker process. When a connection becomes active, theconnection broker hands off the connection to a compatible pooled serverprocess. The pooled server process performs network communication directly onthe client connection and processes requests until the client releases theserver. After being released, the connection is returned to the broker formonitoring, leaving the server free to handle other clients.See Also: Oracle Database ConceptsDatabase instance, Database Resident ConnectionPooling
MARKMark AU for Resynchronization Coordinator ProcessMarks ASM allocation units as stale following amissed write to an offline diskMARK essentially tracks which extents requireresynchronization for offline disks. This process runs in the databaseinstance and is started when the database instance first begins using the ASMinstance. If required, MARK can also be started on demand when disks gooffline in the ASM redundancy disk group.Database and ASM instances
MMANMemory Manager ProcessServes as the instance memory managerThis process performs the resizing of memorycomponents on the instance.Database and ASM instances
MMNLManageability Monitor Lite ProcessPerforms tasks relating to manageability, includingactive session history sampling and metrics computationMMNL performs many tasks relating to manageability,including session history capture and metrics computation.Database and ASM instances
MMONManageability Monitor ProcessPerforms or schedules many manageability tasksMMON performs many tasks related to manageability,including taking Automatic Workload Repository snapshots and performingAutomatic Database Diagnostic Monitor analysis.Database and ASM instances
MnnnMMON Slave ProcessPerforms manageability tasks on behalf of MMONMnnn performs manageability tasksdispatched to them by MMON. Tasks performed include taking Automatic WorkloadRepository snapshots and Automatic Database Diagnostic Monitor analysis.Database and ASM instances
MRP0Managed Standby Recovery ProcessCoordinates the application of redo on a physicalstandby databaseMRP0 is spawned at the start of redo apply on aphysical standby database. This process handles the extraction of redo andcoordinates the application of that redo on a physical standby database.See Also: Oracle Data Guard Concepts and AdministrationDatabase instance, Data Guard
MSnnLogMiner Worker ProcessReads redo log files and translates and assemblesinto transactionsMultiple MSnn processes can exists,where n is 0-9 or a-Z. A minimum of three MSnn processeswork as a group to provide transactions to a LogMiner client, for example, alogical standby database. There may be more than one such group, for example,Downstream Capture sessions.Database instance, Logical Standby, Oracle Streams
NnnnConnection Broker ProcessMonitors idle connections and hands off activeconnections in Database Resident Connection PoolingIn Database Resident Connection Pooling, clientsconnect to a connection broker process. When a connection becomes active, theconnection broker hands off the connection to a compatible pooled serverprocess. The pooled server process performs network communication directly onthe client connection and processes requests until the client releases theserver. After being released, the connection is returned to the broker formonitoring, leaving the server free to handle other clients.See Also: Oracle Database ConceptsDatabase instance, Database Resident ConnectionPooling
NSAnRedo Transport NSA1 ProcessShips redo from current online redo logs to remotestandby destinations configured for ASYNC transportNSAn can run as multiple processes,where n is 1-9 or A-V.See Also: Oracle Data Guard Concepts and AdministrationDatabase instance, Data Guard
NSSnRedo Transport NSS1 ProcessActs as a slave for LGWR when SYNC transport isconfigured for a remote standby destinationNSSn can run as multiple processes,where n is 1-9 or A-V.See Also: Oracle Data Guard Concepts and AdministrationDatabase instance, Data Guard
NSVnData Guard Broker NetSlave ProcessPerforms broker network communications betweendatabases in a Data Guard environmentNSVn is created when a Data Guard brokerconfiguration is enabled. There can be as many NSVn processes(where n is 0- 9 and A-U) created as there are databases inthe Data Guard broker configuration.Database instance, Data Guard
OCFnASM CF Connection Pool ProcessMaintains a connection to the ASM instance formetadata operations Database and ASM instances
OnnnASM Connection Pool ProcessMaintains a connection to the ASM instance formetadata operationsOnnn slave processes are spawned ondemand. These processes communicate with the ASM instance.Database and ASM instances
PINGInterconnect Latency Measurement ProcessAssesses latencies associated with communicationsfor each pair of cluster instancesEvery few seconds, the process in one instance sendsmessages to each instance. The message is received by PING on the targetinstance. The time for the round trip is measured and collected.Database and ASM instances, Oracle RAC
PMONProcess MonitorMonitors the other background processes and performsprocess recovery when a server or dispatcher process terminates abnormallyPMON periodically performs cleanup of all thefollowing:
[*]Processes that died abnormally
[*]Sessions that were killed
[*]Detached transactions that have exceeded their idle timeout
[*]Detached network connections which have exceeded their idle timeout
In addition, PMON monitors, spawns, and stops the following as needed:
[*]Dispatcher and shared server processes
[*]Job queue processes
[*]Pooled server processes for database resident connection pooling
[*]Restartable background processes
PMON is also responsible for registering information about the instanceand dispatcher processes with the network listener.See Also: Oracle Database Concepts and Oracle Database Net Services Administrator's GuideDatabase and ASM instances
PnnnParallel Query Slave ProcessPerform parallel execution of a SQL statement(query, DML, or DDL)Parallel Query has two components: a foregroundprocess that acts as query coordinator and a set of parallel slaves (Pnnn)that are background processes. These background processes are spawned orreused during the start of a parallel statement. They receive and carry outunits of work sent from the query coordinator.The maximum number of Pnnn processes is controlled by theinitialization parameter PARALLEL_MAX_SERVERS. Slave processes are numbered from 0 to the PARALLEL_MAX_SERVERS setting. If the query is aGV$ query, then these background processes are numbered backward,starting from PZ99.Database and ASM instances
PRnnParallel Recovery ProcessPerforms tasks assigned by the coordinator processperforming parallel recoveryPRnn serves as a slave process for thecoordinator process performing parallel media recovery and carries out tasksassigned by the coordinator. The default number of these processes is basedon number of CPUs.Database instance
PSP0Process Spawner ProcessSpawns Oracle background processes after initial instancestartup Database and ASM instances
QMNCAQ Coordinator ProcessMonitors AQQMNC is responsible for facilitating variousbackground activities required by AQ and Oracle Streams: time management ofmessages, management of nonpersistent queues, cleanup of resources, and soon. QMNC dynamically spawns Qnnn processes as needed forperforming these tasks.Note that if the AQ_TM_PROCESSES initialization parameter is set to 0, this process will not start.The database writes the following message to the alert log: WARNING: AQ_TM_PROCESSES isset to 0. System might be adversely affected.Database instance, Advanced Queuing
QnnnAQ Server Class ProcessPerforms various AQ-related background task for QMNCQnnn acts as a slave process for QMNCand carry out tasks assigned by QMNC. The number of these processes isdynamically managed by QMNC based on load.Database instance
RBALASM Rebalance Master ProcessCoordinates rebalance activityIn an ASM instance, it coordinates rebalanceactivity for disk groups. In a database instances, it manages ASM diskgroups.Database and ASM instances
RCBGResult Cache Background ProcessHandles result cache messagesThis process is used for handling invalidation andother messages generated by server processes attached to other instances inOracle RAC.Database instance, Oracle RAC
RECORecoverer ProcessResolves distributed transactions that are pendingbecause of a network or system failure in a distributed databaseRECO uses the information in the pending transactiontable to finalize the status of in-doubt transactions. At timed intervals,the local RECO attempts to connect to remote databases and automaticallycomplete the commit or rollback of the local portion of any pendingdistributed transactions. All transactions automatically resolved by RECO areremoved from the pending transaction table.See Also: Oracle Database Concepts and Oracle Database Net Services Administrator's GuideDatabase instance
RMSnOracle RAC Management ProcessPerforms manageability tasks for Oracle RACRMSn performs a variety of tasks,including creating resources related to Oracle RAC when new instances areadded to a cluster.See Also: Oracle Real Application Clusters Administration andDeployment GuideDatabase instance, Oracle RAC
RnnnASM Block Remap Slave ProcessRemaps a block with a read errorA database instance reading from an ASM disk groupcan encounter an error during a read. If possible, ASM asynchronouslyschedules a Rnnnslave process to remap this bad block from a mirrorcopy.ASM instance
RPnnCapture Processing Worker ProcessProcesses a set of workload capture filesRPnn are worker processes spawned bycallingDBMS_WORKLOAD_REPLAY.PROCESS_CAPTURE(capture_dir,parallel_level). Each worker process is assigned a set of workloadcapture files to process.Worker processes execute in parallel without needing to communicate witheach other. After each process is finished processing its assigned files, itexits and informs its parent process.The number of worker processes is controlled by the parallel_levelparameter of DBMS_WORKLOAD_REPLAY.PROCESS_CAPTURE. By default,parallel_level is null. Then, the number of worker processes is computed asfollows:SELECTVALUE FROM V$PARAMETER WHERENAME='cpu_count';When parallel_level is 1, no worker processes are spawned.Database instance
RSM0Data Guard Broker Worker ProcessPerforms monitoring management tasks related to DataGuard on behalf of DMONThe process is created when a Data Guard brokerconfiguration is enabled.Database instance, Data Guard
RSMNRemote Slave Monitor ProcessManages background slave process creation andcommunication on remote instances in Oracle RACThis background process manages the creation ofslave processes and the communication with their coordinators and peers.These background slave processes perform tasks on behalf of a coordinatingprocess running in another cluster instance.Database instance, Oracle RAC
RVWRRecovery Writer ProcessWrites flashback data to the flashback logs in thefast recovery areaRVWR writes flashback data from the flashback bufferin the SGA to the flashback logs. RVWR also creates flashback logs andperforms some tasks for flashback log automatic management.Database instance, Flashback Database
SMCOSpace Management Coordinator ProcessCoordinates the execution of various spacemanagement tasksThis background process coordinates the execution ofvarious space management tasks, including proactive space allocation andspace reclamation. SMCO dynamically spawns slave processes (Wnnn) toimplement these tasks.Database instance
SMONSystem Monitor ProcessPerforms critical tasks such as instance recoveryand dead transaction recovery, and maintenance tasks such as temporary spacereclamation, data dictionary cleanup, and undo tablespace managementSMON performs many database maintenance tasks,including the following:
[*]Creates and manages the temporary tablespace metadata
[*]Reclaims space used by orphaned temporary segments
[*]Maintains the undo tablespace by onlining, offlining, and shrinking the undo segments based on undo space usage statistics
[*]Cleans up the data dictionary when it is in a transient and inconsistent state
[*]Maintains the SCN to time mapping table used to support Oracle Flashback features
In an Oracle RAC database, the SMON process of one instance can performinstance recovery for other instances that have failed.SMON is resilient to internal and external errors raised during backgroundactivities.See Also: Oracle Database ConceptsDatabase instance
SnnnShared Server ProcessHandles client requests in the shared server architectureIn the shared server architecture, clients connectto a dispatcher process, which creates a virtual circuit for each connection.When the client sends data to the server, the dispatcher receives the datainto the virtual circuit and places the active circuit on the common queue tobe picked up by an idle shared server. The shared server then reads the datafrom the virtual circuit and performs the database work necessary to completethe request. When the shared server must send data to the client, the serverwrites the data back into the virtual circuit and the dispatcher sends thedata to the client. After the shared server completes the client request, theserver releases the virtual circuit back to the dispatcher and is free tohandle other clients.Several initialization parameters relate to shared servers. Theprincipal parameters are: DISPATCHERS, SHARED_SERVERS, MAX_SHARED_SERVERS,LOCAL_LISTENER, REMOTE_LISTENER.See Also: Oracle Database ConceptsDatabase instance, shared servers
TEMnASM disk Test Error Emulation ProcessEmulates I/O errors on ASM disks through named eventsI/O errors can be emulated on ASM disk I/O throughnamed events. The scope can be the process, instance, or even cluster.Optionally, a set of AUs can be chosen for error emulation.ASM instance
VBGnVolume Background ProcessCommunicates between the ASM instance and theoperating system volume driverVBGn handles messages originating fromthe volume driver in the operating system and sends them to the ASM instance.VBGn can run as multiple processes, where n is0-9.ASM instance
VDBGVolume Driver ProcessForwards ASM requests to perform variousvolume-related tasksVDBG handles requests to lock or unlock an extentfor rebalancing, volume resize, disk offline, add or drop a disk, force anddismount disk group to the Dynamic Volume Manager driver.ASM instance
VKRMVirtual Scheduler for Resource Manager ProcessServes as centralized scheduler for Resource ManageractivityVKRM manages the CPU scheduling for all managedOracle processes. The process schedules managed processes in accordance withan active resource plan.Database instance
VKTMVirtual Keeper of Time ProcessProvides a wall clock time and reference time fortime interval measurementsVKTM acts as a time publisher for an Oracleinstance. VKTM publishes two sets of time: a wall clock time using a secondsinterval and a higher resolution time (which is not wall clock time) forinterval measurements. The VKTM timer service centralizes time tracking andoffloads multiple timer calls from other clients.Database and ASM instances
VMB0Volume Membership ProcessMaintains cluster membership on behalf of the ASMvolume driverThis process membership in the cluster as anI/O-capable client on behalf of the ASM volume driver.ASM instance
VnnnASM Volume I/O Slave ProcessInitializes ASM volume contents during creationThis process is responsible for initializing the ASMvolume during creation.ASM instance
WnnnSpace Management Slave ProcessPerforms various background space management tasks,including proactive space allocation and space reclamationWnnn processes are slave processesdynamically spawned by SMCO to perform space management tasks in thebackground. These tasks include preallocating space into locally managedtablespace and SecureFiles segments based on space usage growth analysis, andreclaiming space from dropped segments. At most 10 Wnnn slavescan run on one database instance. After being started, the slave acts as anautonomous agent. After it finishes task execution, it automatically picks upanother task from the queue. The process terminates itself after being idlefor a long time.Database instance
XDMGExadata Automation ManagerInitiates automation tasks involved in managingExadata storageXDMG monitors all configured Exadata cells for statechanges, such as a bad disk getting replaced, and performs the required tasksfor such events. Its primary tasks are to watch for inaccessible disks andcells and when they become accessible again, and to initiate the ASM ONLINEoperation. The ONLINE operation is handled by XDWK.ASM instance, Exadata
XDWKExadata Automation ManagerPerforms automation tasks requested by XDMGXDWK gets started when asynchronous actions such asONLINE, DROP, and ADD an ASM disk are requested by XDMG. After a 5 minuteperiod of inactivity, this process will shut itself down.ASM instance, Exadata
XnnnASM Disk Expel Slave ProcessPerforms ASM post-rebalance activitiesThis process expels dropped disks at the end of anASM rebalance.ASM instance
*ACMS (atomiccontrolfile to memory service) per-instance process is an agent thatcontributes to ensuring a distributed SGA memory update is either globallycommitted on success or globally aborted in the event of a failure in an OracleRAC environment.
*DBRM (database resource manager) process isresponsible for setting resource plans and other resource manager relatedtasks.
* DIA0 (diagnosabilityprocess 0) (only 0 is currently being used) is responsible for hang detectionand deadlock resolution. *DIAG (diagnosability)process performs diagnostic dumps and executes global oradebug commands.*EMNC (eventmonitor coordinator) is the background server process used for database eventmanagement and notifications. *FBDA (flashbackdata archiver process) archives the historical rows of tracked tables intoflashback data archives. Tracked tables are tables which are enabled forflashback archive. When a transaction containing DML on a tracked tablecommits, this process stores the pre-image of the rows into the flashbackarchive. It also keeps metadata on the current rows.
FBDA is also responsible for automatically managing the flashback data archivefor space, organization, and retention and keeps track of how far the archivingof tracked transactions has occurred.
*GTX0-j (global transaction) processes providetransparent support for XA global transactions in an Oracle RAC environment.The database autotunes the number of these processes based on the workload ofXA global transactions. Global transaction processes are only seen in an OracleRAC environment. *KATE performsproxy I/O to an ASM metafile when a disk goes offline. *MARK marksASM allocation units as stale following a missed write to an offline disk. *SMCO (spacemanagement coordinator) process coordinates the execution of various spacemanagement related tasks, such as proactive space allocation and spacereclamation. It dynamically spawns slave processes (Wnnn) to implement thetask.
*VKTM (virtual keeper of time) is responsible forproviding a wall-clock time (updated every second) and reference-time counter(updated every 20 ms and available only when running at elevated priority) * PZ (PQ slaves used for global Views)are RAC Parallel Server Slave processes, but they are not normal parallel slaveprocesses, PZnn processes (starting at 99) are used to query GV$ views which isdone using Parallel Execution on all instances, if more than one PZ process isneeded, then PZ98, PZ97,... (in that order) are created automatically. * O00 (ASM slave processes) A group ofslave processes establish connections to the ASM instance. Through thisconnection pool database processes can send messages to the ASM instance. Forexample opening a file sends the open request to the ASM instance via a slave.However slaves are not used for long running operations such as creating afile. The use slave (pool) connections eliminate the overhead oflogginginto the ASM instance for short requests * x000 - Slave used to expell disks afterdiskgroup reconfiguration 学习了~
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