Oracle 11g后台进程一览表

发布时间：2020-12-12 14:05:22 所属栏目：百科来源：网络整理

导读：Background Processes Table F-1describes Oracle Database background processes. In this context,a background process is defined as any process that is listed in V$PROCESS and has a non-null value in the pname column. The External Properties

ABMR

Auto BMR Background Process

Coordinates execution of tasks such as filtering duplicate block media recovery requests and performing flood control

When a process submits a block media recovery request to ABMR,it dynamically spawns slave processes (BMRn) to perform the recovery. ABMR and BMRnterminate after being idle for a long time.

See Also:Oracle Database Backup and Recovery User's Guide

Database instance

ACFS

ASM Cluster File System CSS Process

Tracks the cluster membership in CSS and informs the file system driver of membership changes

ACFS delivers CSS membership changes to the Oracle cluster file system. These membership changes are required for the file system to maintain file system consistency within the cluster.

ASM instance,Oracle RAC

ACMS

Atomic Control File to Memory Service Process

Coordinates consistent updates to a control file resource with its SGA counterpart on all instances in an Oracle RAC environment

The ACMS process works with a coordinating caller to ensure that an operation is executed on every instance in Oracle RAC despite failures. ACMS is the process in which a distributed operation is called. As a result,this process can exhibit a variety of behaviors. In general,ACMS is limited to small,nonblocking state changes for a limited set of cross-instance operations.

Database instance,Oracle RAC

APnn

Logical Standby / Streams Apply Process Coordinator Process

Obtains transactions from the reader server and passes them to apply servers

The coordinator process name is APnn,wherenncan include letters and numbers.

See Also:Oracle Streams Concepts and Administration

Database instance,Data Guard,Oracle Streams

ARBn

ASM Rebalance Process

Rebalances data extents within an ASM disk group

Possible processes are ARB0-ARB9 and ARBA.

ASM instance

ARCn

Archiver Process

Copies the redo log files to archival storage when they are full or an online redo log switch occurs

ARCnprocesses exist only when the database is inARCHIVELOGmode and automatic archiving is enabled,in which case ARCnautomatically archives online redo log files. LGWR cannot reuse and overwrite an online redo log group until it has been archived.

The database starts multiple archiver processes as needed to ensure that the archiving of filled online redo logs does not fall behind. Possible processes include ARC0-ARC9 and ARCa-ARCt.

TheLOG_ARCHIVE_MAX_PROCESSESinitialization parameter specifies the number of ARCnprocesses that the database initially invokes.

See Also:Oracle Database ConceptsandOracle Database Administrator's Guide

Database instance

ASMB

ASM Background Process

Communicates with the ASM instance,managing storage and providing statistics

ASMB runs in ASM instances when the ASMCMDcpcommand runs or when the database instance first starts if the server parameter file is stored in ASM. ASMB also runs with Oracle Cluster Registry on ASM.

Database and ASM instances

ASnn

Logical Standby / Streams Apply Process Reader Server 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 computing dependencies between LCRs and assembling transactions,it returns the assembled transactions to the coordinator process. QueryV$STREAMS_APPLY_READERfor information about the reader server background process.

An apply server receives the transactions from the coordinator background process,and either applies database changes in LCRs or sends LCRs or messages to apply handlers. Apply servers can also enqueue a queue. If an apply server encounters an error,then it then tries to resolve the error with a user-specified conflict handler or error handler. If an apply server cannot resolve an error,then it rolls back the transaction and places the entire transaction,including all of its messages,in the error queue. When an apply server commits a completed transaction,this transaction has been applied. When an apply server places a transaction in the error queue and commits,this transaction also has been applied. QueryV$STREAMS_APPLY_SERVERfor information about the apply server background process.

The coordinator process name is ASnn,wherenncan include letters and numbers.

Database instance

BMRn

Automatic Block Media Recovery Slave Pool Process

Fetches blocks from a real-time readable standby database

When a process submits a block media recovery request to ABMR,it dynamically spawns slave processes (BMRn) to perform the recovery. BMRnprocesses fetch blocks from a real-time readable standby database. ABMR and BMRnterminate after being idle for a long time.

See Also:Oracle Database Backup and Recovery User's Guide

Database instance

Bnnn

ASM Blocking Slave Process for GMON

Performs maintenance actions on ASM disk groups

Bnnnperforms actions that require waiting for resources on behalf of GMON. GMON must be highly available and cannot wait.

A Bnnnslave is spawned when a disk is taken offline in an ASM disk group. Offline timer processing and drop of the disk are performed in this slave. Up to five process (B000 to B004) can exist depending on the load.

ASM instance

CJQ0

Job Queue Coordinator Process

Selects jobs that need to be run from the data dictionary and spawns job queue slave processes (Jnnn) to run the jobs

CJQ0 is automatically started and stopped as needed by Oracle Scheduler.

TheJOB_QUEUE_PROCESSESinitialization parameter specifies the maximum number of processes that can be created for the execution of jobs. CJQ0 starts only as many job queue processes as required by the number of jobs to run and available resources.

See Also:Oracle Database ConceptsandOracle Database Administrator's Guide

Database instance

CKPT

Checkpoint Process

Signals DBWnat checkpoints and updates all the data files and control files of the database to indicate the most recent checkpoint

At specific times CKPT starts a checkpoint request by messaging DBWnto begin writing dirty buffers. On completion of individual checkpoint requests,CKPT updates data file headers and control files to record most recent checkpoint.

See Also:

CSnn

Streams Propagation Sender Process

Sends LCRs to a propagation receiver

The propagation sender process name is CSnn,wherenncan include letters and numbers. In an Oracle Streams combined capture and apply optimization,the propagation sender sends LCRs directly to the propagation receiver to improve performance. The propagation receiver passes the LCRs to an apply process. QueryV$PROPAGATION_SENDERfor information about a propagation sender.

Database instance,Oracle Streams

CSnn

I/O Calibration Process

Issues I/Os to storage as part of storage calibration.

CSnnslave processes are started on execution of theDBMS_RESOURCE_MANAGER.CALIBRATE_IO()procedure. There is one slave process per CPU on each node of the database.

Database instance,Oracle RAC

CTWR

Change Tracking Writer Process

Tracks changed data blocks as part of the Recovery Manager block change tracking feature

CTWR tracks changed blocks as redo is generated at a primary database and as redo is applied at a standby database. The process is slightly different depending on the type of database.

See Also:Oracle Database Backup and Recovery User's Guide

Database instance

DBRM

Database Resource Manager Process

Sets resource plans and performs other tasks related to the Database Resource Manager

If a resource plan is not enabled,then this process is idle.

See Also:Oracle Database Administrator's Guide

Database instance

DBWn

Database Writer Process

Writes modified blocks from the database buffer cache to the data files

The primary responsibility of DBWnis to write data blocks to disk. DBWnalso handles checkpoints,file open synchronization,and logging of Block Written records.

In many cases the blocks that DBWnwrites are scattered throughout the disk. Thus,the writes tend to be slower than the sequential writes performed by LGWR. DBWnperforms multiblock writes when possible to improve efficiency. The number of blocks written in a multiblock write varies by operating system.

TheDB_WRITER_PROCESSESinitialization parameter specifies the number of DBWnprocesses (DBW0-DBW9 and DBWa-DBWz). The database selects an appropriate default setting for this parameter or adjusts a user-specified setting based on the number of CPUs and processor groups.

See Also:Oracle Database ConceptsandOracle Database Performance Tuning Guide

Database instance

DIA0

Diagnostic Process

Detects and resolves hangs and deadlocks

ASM and Database instances

DIAG

Diagnostic Capture Process

Performs diagnostic dumps
DIAG performs diagnostic dumps requested by other processes and dumps triggered by process or instance termination. In Oracle RAC,DIAG performs global diagnostic dumps requested by remote instances.

ASM and Database instances

DMnn

Data Pump Master Process

Coordinates the Data Pump job tasks performed by Data Pump worker processes and handles client interactions

The Data Pump master (control) process is started during job creation and coordinates all tasks performed by the Data Pump job. It handles all client interactions and communication,establishes all job contexts,and coordinates all worker process activities on behalf of the job.

Database instance,Data Pump

DMON

Data Guard Broker Monitor Process

Manages and monitors a database that is part of a Data Guard broker configuration

When you start the Data Guard broker,a DMON process is created. DMON runs for every database instance that is managed by the broker. DMON interacts with the local database and the DMON processes of the other databases to perform the requested function. DMON also monitors the health of the broker configuration and ensures that every database has a consistent description of the configuration.

DMON maintains profiles about all database objects in the broker configuration in a binary configuration file. A copy of this file is maintained by the DMON process for each of the databases that belong to the broker configuration. The process is created when theDG_BROKER_STARTinitialization parameter is set totrue.

See Also:

LSP0

Logical Standby Coordinator Process

Schedules transactions for Data Guard SQL Apply

LSP0 is the initial process created upon startup of Data Guard SQL Apply. In addition to managing LogMiner and Apply processes,LSP0 is responsible for maintaining inter-transaction dependencies and appropriately scheduling transactions with applier processes. LSP0 is also responsible for detecting and enabling runtime parameter changes for the SQL Apply product as a whole.

Database instance,Data Guard

LSP1

Logical Standby Dictionary Build Process

Performs a logical standby dictionary build on a primary database

The LSP1 process is spawned on a logical standby database that is intended to become the new primary database. A logical standby database becomes a primary database by means of switchover or failover. The dictionary is necessary for logical standby databases to interpret the redo of the new primary database.

Database instance,Data Guard

LSP2

Logical Standby Set Guard Process

Determines which database objects will be protected by the database guard

The LSP2 process is created as needed during startup of SQL Apply to update the list of objects that are protected by the database guard.

Database instance,Data Guard

Lnnn

Pooled Server Process

Handles client requests in Database Resident Connection Pooling

In Database Resident Connection Pooling,clients connect to a connection broker process. When a connection becomes active,the connection broker hands off the connection to a compatible pooled server process. The pooled server process performs network communication directly on the client connection and processes requests until the client releases the server. After being released,the connection is returned to the broker for monitoring,leaving the server free to handle other clients.

See Also:

MARK

Mark AU for Resynchronization Coordinator Process

Marks ASM allocation units as stale following a missed write to an offline disk

MARK essentially tracks which extents require resynchronization for offline disks. This process runs in the database instance and is started when the database instance first begins using the ASM instance. If required,MARK can also be started on demand when disks go offline in the ASM redundancy disk group.

Database and ASM instances

MMAN

Memory Manager Process

Serves as the instance memory manager

This process performs the resizing of memory components on the instance.

Database and ASM instances

MMNL

Manageability Monitor Lite Process

Performs tasks relating to manageability,including active session history sampling and metrics computation

MMNL performs many tasks relating to manageability,including session history capture and metrics computation.

Database and ASM instances

MMON

Manageability Monitor Process

Performs or schedules many manageability tasks

MMON performs many tasks related to manageability,including taking Automatic Workload Repository snapshots and performing Automatic Database Diagnostic Monitor analysis.

Database and ASM instances

Mnnn

MMON Slave Process

Performs manageability tasks on behalf of MMON

Mnnnperforms manageability tasks dispatched to them by MMON. Tasks performed include taking Automatic Workload Repository snapshots and Automatic Database Diagnostic Monitor analysis.

Database and ASM instances

MRP0

Managed Standby Recovery Process

Coordinates the application of redo on a physical standby database

MRP0 is spawned at the start of redo apply on a physical standby database. This process handles the extraction of redo and coordinates the application of that redo on a physical standby database.

See Also:Oracle Data Guard Concepts and Administration

Database instance,Data Guard

MSnn

LogMiner Worker Process

Reads redo log files and translates and assembles into transactions

Multiple MSnnprocesses can exists,wherenis 0-9 or a-Z. A minimum of three MSnnprocesses work as a group to provide transactions to a LogMiner client,for example,a logical standby database. There may be more than one such group,Downstream Capture sessions.

Database instance,Logical Standby,Oracle Streams

Nnnn

Connection Broker Process

Monitors idle connections and hands off active connections in Database Resident Connection Pooling

In Database Resident Connection Pooling,Database Resident Connection Pooling

NSAn

Redo Transport NSA1 Process

Ships redo from current online redo logs to remote standby destinations configured for ASYNC transport

NSAncan run as multiple processes,wherenis 1-9 or A-V.

See Also:

NSSn

Redo Transport NSS1 Process

Acts as a slave for LGWR when SYNC transport is configured for a remote standby destination

NSSncan run as multiple processes,Data Guard

NSVn

Data Guard Broker NetSlave Process

Performs broker network communications between databases in a Data Guard environment

NSVnis created when a Data Guard broker configuration is enabled. There can be as many NSVnprocesses (wherenis 0- 9 and A-U) created as there are databases in the Data Guard broker configuration.

Database instance,Data Guard

OCFn

ASM CF Connection Pool Process

Maintains a connection to the ASM instance for metadata operations

Database and ASM instances

Onnn

ASM Connection Pool Process

Maintains a connection to the ASM instance for metadata operations

Onnnslave processes are spawned on demand. These processes communicate with the ASM instance.

Database and ASM instances

PING

Interconnect Latency Measurement Process

Assesses latencies associated with communications for each pair of cluster instances

Every few seconds,the process in one instance sends messages to each instance. The message is received by PING on the target instance. The time for the round trip is measured and collected.

Database and ASM instances,Oracle RAC

PMON

Process Monitor

Monitors the other background processes and performs process recovery when a server or dispatcher process terminates abnormally

PMON periodically performs cleanup of all the following:

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 instance and dispatcher processes with the network listener.

See Also:Oracle Database ConceptsandOracle Database Net Services Administrator's Guide

Database and ASM instances

Pnnn

Parallel Query Slave Process

Perform parallel execution of a SQL statement (query,DML,or DDL)

Parallel Query has two components: a foreground process that acts as query coordinator and a set of parallel slaves (Pnnn) that are background processes. These background processes are spawned or reused during the start of a parallel statement. They receive and carry out units of work sent from the query coordinator.

The maximum number of Pnnnprocesses is controlled by the initialization parameterPARALLEL_MAX_SERVERS. Slave processes are numbered from 0 to thePARALLEL_MAX_SERVERSsetting. If the query is aGV$query,then these background processes are numbered backward,starting from PZ99.

Database and ASM instances

PRnn

Parallel Recovery Process

Performs tasks assigned by the coordinator process performing parallel recovery

PRnnserves as a slave process for the coordinator process performing parallel media recovery and carries out tasks assigned by the coordinator. The default number of these processes is based on number of CPUs.

Database instance

PSP0

Process Spawner Process

Spawns Oracle background processes after initial instance startup

Database and ASM instances

QMNC

AQ Coordinator Process

Monitors AQ

QMNC is responsible for facilitating various background activities required by AQ and Oracle Streams: time management of messages,management of nonpersistent queues,cleanup of resources,and so on. QMNC dynamically spawns Qnnnprocesses as needed for performing these tasks.

Note that if theAQ_TM_PROCESSESinitialization parameter is set to 0,this process will not start. The database writes the following message to the alert log:WARNING: AQ_TM_PROCESSES is set to 0. System might be adversely affected.

Database instance,Advanced Queuing

Qnnn

AQ Server Class Process

Performs various AQ-related background task for QMNC

Qnnnacts as a slave process for QMNC and carry out tasks assigned by QMNC. The number of these processes is dynamically managed by QMNC based on load.

Database instance

RBAL

ASM Rebalance Master Process

Coordinates rebalance activity

In an ASM instance,it coordinates rebalance activity for disk groups. In a database instances,it manages ASM disk groups.

Database and ASM instances

RCBG

Result Cache Background Process

Handles result cache messages

This process is used for handling invalidation and other messages generated by server processes attached to other instances in Oracle RAC.

Database instance,Oracle RAC

RECO

Recoverer Process

Resolves distributed transactions that are pending because of a network or system failure in a distributed database

RECO uses the information in the pending transaction table to finalize the status of in-doubt transactions. At timed intervals,the local RECO attempts to connect to remote databases and automatically complete the commit or rollback of the local portion of any pending distributed transactions. All transactions automatically resolved by RECO are removed from the pending transaction table.

See Also:Oracle Database Net Services Administrator's Guide

Database instance

RMSn

Oracle RAC Management Process

Performs manageability tasks for Oracle RAC

RMSnperforms a variety of tasks,including creating resources related to Oracle RAC when new instances are added to a cluster.

See Also:

Rnnn

ASM Block Remap Slave Process

Remaps a block with a read error

A database instance reading from an ASM disk group can encounter an error during a read. If possible,ASM asynchronously schedules a Rnnnslave process to remap this bad block from a mirror copy.

ASM instance

RPnn

Capture Processing Worker Process

Processes a set of workload capture files

RPnnare worker processes spawned by callingDBMS_WORKLOAD_REPLAY.PROCESS_CAPTURE(capture_dir,parallel_level). Each worker process is assigned a set of workload capture files to process.

Worker processes execute in parallel without needing to communicate with each other. After each process is finished processing its assigned files,it exits and informs its parent process.

The number of worker processes is controlled by theparallel_levelparameter ofDBMS_WORKLOAD_REPLAY.PROCESS_CAPTURE. By default,parallel_levelis null. Then,the number of worker processes is computed as follows:

SELECT VALUE 
FROM   V$PARAMETER 
WHERE  NAME='cpu_count';

Whenparallel_levelis1,no worker processes are spawned.

Database instance

RSM0

Data Guard Broker Worker Process

Performs monitoring management tasks related to Data Guard on behalf of DMON

The process is created when a Data Guard broker configuration is enabled.

Database instance,Data Guard

RSMN

Remote Slave Monitor Process

Manages background slave process creation and communication on remote instances in Oracle RAC

This background process manages the creation of slave processes and the communication with their coordinators and peers. These background slave processes perform tasks on behalf of a coordinating process running in another cluster instance.

Database instance,Oracle RAC

RVWR

Recovery Writer Process

Writes flashback data to the flashback logs in the flash recovery area

RVWR writes flashback data from the flashback buffer in the SGA to the flashback logs. RVWR also creates flashback logs and performs some tasks for flashback log automatic management.

Database instance,Flashback Database

SMCO

Space Management Coordinator Process

Coordinates the execution of various space management tasks

This background process coordinates the execution of various space management tasks,including proactive space allocation and space reclamation. SMCO dynamically spawns slave processes (Wnnn) to implement these tasks.

Database instance

SMON

System Monitor Process

Performs critical tasks such as instance recovery and dead transaction recovery,and maintenance tasks such as temporary space reclamation,data dictionary cleanup,and undo tablespace management

SMON 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 perform instance recovery for other instances that have failed.

SMON is resilient to internal and external errors raised during background activities.

Name	Expanded Name	Short Description	Long Description	External Properties
Background Processes Table F-1describes Oracle Database background processes. In this context,abackground processis defined as any process that is listed in`V$PROCESS`and has a non-null value in the`pname`column. The External Properties column lists the type of instance in which the process runs. If the process is specific to a particular feature,then the column names the feature. Table F-1 Background Processes

Background Processes

Table F-1describes Oracle Database background processes. In this context,abackground processis defined as any process that is listed inV$PROCESSand has a non-null value in thepnamecolumn.

The External Properties column lists the type of instance in which the process runs. If the process is specific to a particular feature,then the column names the feature.

Table F-1 Background Processes

Name Expanded Name Short Description Long Description External Properties