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  • Oracle 11g后台进程一览表

    Background Processes

    Table F-1 describes 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 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

    NameExpanded NameShort DescriptionLong DescriptionExternal 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 BMRn terminate 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, where nn can 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

    ARCn processes exist only when the database is in ARCHIVELOG mode and automatic archiving is enabled, in which case ARCn automatically 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.

    The LOG_ARCHIVE_MAX_PROCESSES initialization parameter specifies the number of ARCn processes that the database initially invokes.

    See Also: Oracle Database Concepts and Oracle 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 ASMCMD cp command 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. Query V$STREAMS_APPLY_READER for 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. Query V$STREAMS_APPLY_SERVER for information about the apply server background process.

    The coordinator process name is ASnn, where nn can 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. BMRn processes fetch blocks from a real-time readable standby database. ABMR and BMRn terminate 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

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

    A Bnnn slave 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.

    The JOB_QUEUE_PROCESSES initialization 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 Concepts and Oracle Database Administrator's Guide

    Database instance

    CKPT

    Checkpoint Process

    Signals DBWn at 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 DBWn to 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: Oracle Database Concepts

    Database and ASM instances

    CPnn

    Streams Capture Process

    Captures database changes from the redo log by using the infrastructure of LogMiner

    The capture process name is CPnn, where nn can include letters and numbers. The underlying LogMiner process name is MSnn, where nn can include letters and numbers. The capture process includes one reader server that reads the redo log and divides it into regions, one or more preparer servers that scan the redo log, and one builder server that merges redo records from the preparer servers. Each reader server, preparer server, and builder server is a process. Query the V$STREAMS_CAPTUREview for information about this background process.

    See Also: Oracle Streams Concepts and Administration

    Database instance, Oracle Streams

    CSnn

    Streams Propagation Sender Process

    Sends LCRs to a propagation receiver

    The propagation sender process name is CSnn, where nn can 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. Query V$PROPAGATION_SENDER for information about a propagation sender.

    Database instance, Oracle Streams

    CSnn

    I/O Calibration Process

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

    CSnn slave processes are started on execution of the DBMS_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 DBWn is to write data blocks to disk. DBWn also handles checkpoints, file open synchronization, and logging of Block Written records.

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

    The DB_WRITER_PROCESSES initialization parameter specifies the number of DBWn processes (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 Concepts and Oracle 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 the DG_BROKER_START initialization parameter is set to true.

    See Also: Oracle Data Guard Broker

    Database instance, Data Guard

    Dnnn

    Dispatcher Process

    Performs network communication in the shared server architecture

    In the shared server architecture, clients connect to a dispatcher process, which creates a virtual circuit for each connection. When the client sends data to the server, the dispatcher receives the data into the virtual circuit and places the active circuit on the common queue to be picked up by an idle shared server. The shared server then reads the data from the virtual circuit and performs the database work necessary to complete the request. When the shared server must send data to the client, the server writes the data back into the virtual circuit and the dispatcher sends the data to the client. After the shared server completes the client request, the server releases the virtual circuit back to the dispatcher and is free to handle other clients.

    Several initialization parameters relate to shared servers. The principal parameters are: DISPATCHERS, SHARED_SERVERS, MAX_SHARED_SERVERS, LOCAL_LISTENER, REMOTE_LISTENER.

    See Also: Oracle Database Concepts

    Database instance, shared servers

    DRnn

    ASM Disk Resynchronization Slave Process

    Resynchronizes the contents of an offline disk

    When a disk online SQL command is issued on a disk or disks that are offline, ASM spawns DRnn. Depending on the load, more than one slave may be spawned.

    ASM Instance

    DSKM

    Slave Diskmon Process

    Acts as the conduit between the database, ASM instances, and the Master Diskmon daemon to communicate information to Exadata storage

    This process is active only if Exadata Storage is used. DSKM performs operations related to Exadata I/O fencing and Exadata cell failure handling.

    ASM instance, Exadata

    DWnn

    Data Pump Worker Process

    Performs Data Pump tasks as assigned by the Data Pump master process

    The Data Pump worker process is responsible for performing tasks that are assigned by the Data Pump master process, such as the loading and unloading of metadata and data.

    Database instance

    EMNC

    EMON Coordinator Process

    Coordinates database event management and notifications

    EMNC coordinates event management and notification activity in the database, including Streams Event Notifications, Continuous Query Notifications, and Fast Application Notifications.

    Database and ASM instances

    Ennn

    EMON Slave Process

    Performs database event management and notifications

    The database event management and notification load is distributed among the EMON slave processes. These processes work on the system notifications in parallel, offering a capability to process a larger volume of notifications, a faster response time, and a lower shared memory use for staging notifications.

    Database and ASM instances

    FBDA

    Flashback Data Archiver Process

    Archives historical rows for tracked tables into flashback data archives and manages archive space, organization, and retention

    When a transaction that modifies a tracked table commits, FBDA stores the pre-image of the rows in the archive. FDBA maintains metadata on the current rows and tracks how much data has been archived.

    FBDA is also responsible for automatically managing the flashback data archive for space, organization (partitioning tablespaces), and retention. FBDA also keeps track of how far the archiving of tracked transactions has progressed.

    See Also: Oracle Database Advanced Application Developer's Guide

    Database and ASM instances

    FMON

    File Mapping Monitor Process

    Manages mapping information for the Oracle Database file mapping interface

    The DBMS_STORAGE_MAP package enables you to control the mapping operations. When instructed by the user, FMON builds mapping information and stores it in the SGA, refreshes the information when a change occurs, saves the information to the 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

    FSFP

    Data Guard Broker Fast Start Failover Pinger Process

    Maintains fast-start failover state between the primary and target standby databases

    FSFP is created when fast-start failover is enabled.

    Database instance, Data Guard

    GCRnFoot 1 

    Global Conflict Resolution Slave Process

    Performs synchronous tasks on behalf of LMHB

    GCRn processes are transient slaves that are started and stopped as required by LMHB to perform synchronous or resource intensive tasks.

    Database and ASM instances, Oracle RAC

    GEN0

    General Task Execution Process

    Performs required tasks including SQL and DML

    		  

    Database and ASM instances

    GMON

    ASM Disk Group Monitor Process

    Monitors all mounted ASM disk groups

    GMON monitors all the disk groups mounted in an ASM instance and is responsible for maintaining consistent disk membership and status information. Membership changes result from adding and dropping disks, whereas disk status changes result from taking disks offline or bringing them online.

    ASM instance

    GTXn

    Global Transaction Process

    Provides transparent support for XA global transactions in an Oracle RAC environment

    These processes help maintain the global information about XA global transactions throughout the cluster. Also, the processes help perform two-phase commit for global transactions anywhere in the cluster so that an Oracle RAC database behaves as a single system to the externally coordinated distributed transactions.

    The GLOBAL_TXN_PROCESSES initialization parameter specifies the number of GTXn processes, where n is 0-9 or a-j. The database automatically tunes the number of these processes based on the workload of XA global transactions. You can disable these processes by setting the parameter to 0. If you try to run XA global transactions with these process disabled, an error is returned.

    See Also: Oracle Real Application Clusters Administration and Deployment Guide

    Database instance, Oracle RAC

    Innn

    Disk and Tape I/O Slave Process

    Serves as an I/O slave process spawned on behalf of DBWR, LGWR, or an RMAN backup session

    I/O slave process can be configured on platforms where asynchronous I/O support is not available. These slaves are started by setting the corresponding slave enable parameter in the server parameter file. The I/O slaves simulate the asynchronous I/O behavior when the underlying platform does not have native support for asynchronous I/O.

    Database instance

    INSV

    Data Guard Broker Instance Slave Process

    Performs Data Guard broker communication among instances in an Oracle RAC environment

    INSV is created when the DG_BROKER_START initialization parameter is set to true.

    Database instance, Data Guard

    Jnnn

    Job Queue Slave Process

    Executes jobs assigned by the job coordinator

    Job slave processes are created or awakened by the job coordinator when it is time for a job to be executed.

    Job slaves gather all the metadata required to run the job from the data dictionary. The slave processes start a database session as the owner of the job, execute triggers, and then execute the job. After the job is complete, the slave processes commit and then execute appropriate triggers and close the session. The slave can repeat this operation in case additional jobs need to be run.

    Database instance

    LCK0

    Instance Enqueue Background Process

    Manages global enqueue requests and cross-instance broadcasts

    The process handles all requests for resources other than data blocks. For examples, LCK0 manages library and row cache requests.

    Database and ASM instances, Oracle RAC

    LGWR

    Log Writer Process

    Writes redo entries to the online redo log

    Redo log entries are generated in the redo log buffer of the system global area (SGA). LGWR writes the redo log entries sequentially into a redo log file. If the database has a multiplexed redo log, then LGWR writes the redo log entries to a group of redo log files.

    See Also: Oracle Database Concepts and Oracle Database Administrator's Guide

    Database and ASM instances

    LMD0

    Global Enqueue Service Daemon 0 Process

    Manages incoming remote resource requests from other instances

    LMD0 processes enqueue resources managed under Global Enqueue Service. In particular, LMD0 processes incoming enqueue request messages and controls access to global enqueues. It also performs distributed deadlock detections.

    Database and ASM instances, Oracle RAC

    LMHB

    Global Cache/Enqueue Service Heartbeat Monitor

    Monitor the heartbeat of LMON, LMD, and LMSn processes

    LMHB monitors LMON, LMD, and LMSn processes to ensure they are running normally without blocking or spinning.

    Database and ASM instances, Oracle RAC

    LMON

    Global Enqueue Service Monitor Process

    Monitors an Oracle RAC cluster to manage global resources

    LMON maintains instance membership within Oracle RAC. The process detects instance transitions and performs reconfiguration of GES and GCS resources.

    See Also: Oracle Real Application Clusters Administration and Deployment Guide

    Database and ASM instances, Oracle RAC

    LMSn

    Global Cache Service Process

    Manages resources and provides resource control among Oracle RAC instances

    LMS, where n is 0-9 or a-z, maintains a lock database for Global Cache Service (GCS) and buffer cache resources. This process receives, processes, and sends GCS requests, block transfers, and other GCS-related messages.

    See Also: Oracle Real Application Clusters Administration and Deployment Guide

    Database and ASM instances, Oracle RAC

    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: Oracle Database Concepts

    Database instance, Database Resident Connection Pooling

    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

    Mnnn performs 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 MSnn processes can exists, where n is 0-9 or a-Z. A minimum of three MSnn processes 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, for example, 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, 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: Oracle Database Concepts

    Database instance, Database Resident Connection Pooling

    NSAn

    Redo Transport NSA1 Process

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

    NSAn can run as multiple processes, where n is 1-9 or A-V.

    See Also: Oracle Data Guard Concepts and Administration

    Database instance, Data Guard

    NSSn

    Redo Transport NSS1 Process

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

    NSSn can run as multiple processes, where n is 1-9 or A-V.

    See Also: Oracle Data Guard Concepts and Administration

    Database instance, Data Guard

    NSVn

    Data Guard Broker NetSlave Process

    Performs broker network communications between databases in a Data Guard environment

    NSVn is created when a Data Guard broker configuration is enabled. There can be as many NSVn processes (where n is 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

    Onnn slave 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 Concepts and Oracle 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 Pnnn processes is controlled by the initialization parameter PARALLEL_MAX_SERVERS. Slave processes are numbered from 0 to the PARALLEL_MAX_SERVERS setting. If the query is a GV$ 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

    PRnn serves 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 Qnnn processes as needed for performing 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 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

    Qnnn acts 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 Concepts and Oracle Database Net Services Administrator's Guide

    Database instance

    RMSn

    Oracle RAC Management Process

    Performs manageability tasks for Oracle RAC

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

    See Also: Oracle Real Application Clusters Administration and Deployment Guide

    Database instance, Oracle RAC

    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 Rnnn slave process to remap this bad block from a mirror copy.

    ASM instance

    RPnn

    Capture Processing Worker Process

    Processes a set of workload capture files

    RPnn are worker processes spawned by calling DBMS_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 the parallel_level parameter of DBMS_WORKLOAD_REPLAY.PROCESS_CAPTURE. By default, parallel_level is null. Then, the number of worker processes is computed as follows:

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

    When parallel_level is 1, 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.

    See Also: Oracle Database Concepts

    Database instance

    Snnn

    Shared Server Process

    Handles client requests in the shared server architecture

    In the shared server architecture, clients connect to a dispatcher process, which creates a virtual circuit for each connection. When the client sends data to the server, the dispatcher receives the data into the virtual circuit and places the active circuit on the common queue to be picked up by an idle shared server. The shared server then reads the data from the virtual circuit and performs the database work necessary to complete the request. When the shared server must send data to the client, the server writes the data back into the virtual circuit and the dispatcher sends the data to the client. After the shared server completes the client request, the server releases the virtual circuit back to the dispatcher and is free to handle other clients.

    Several initialization parameters relate to shared servers. The principal parameters are: DISPATCHERS, SHARED_SERVERS, MAX_SHARED_SERVERS, LOCAL_LISTENER, REMOTE_LISTENER.

    See Also: Oracle Database Concepts

    Database instance, shared servers

    TEMn

    ASM disk Test Error Emulation Process

    Emulates I/O errors on ASM disks through named events

    I/O errors can be emulated on ASM disk I/O through named events. The scope can be the process, instance, or even cluster. Optionally, a set of AUs can be chosen for error emulation.

    ASM instance

    VBGn

    Volume Background Process

    Communicates between the ASM instance and the operating system volume driver

    VBGn handles messages originating from the volume driver in the operating system and sends them to the ASM instance.

    VBGn can run as multiple processes, where n is 0-9.

    ASM instance

    VDBG

    Volume Driver Process

    Forwards ASM requests to perform various volume-related tasks

    VDBG handles requests to lock or unlock an extent for rebalancing, volume resize, disk offline, add or drop a disk, force and dismount disk group to the Dynamic Volume Manager driver.

    ASM instance

    VKRM

    Virtual Scheduler for Resource Manager Process

    Serves as centralized scheduler for Resource Manager activity

    VKRM manages the CPU scheduling for all managed Oracle processes. The process schedules managed processes in accordance with an active resource plan.

    Database instance

    VKTM

    Virtual Keeper of Time Process

    Provides a wall clock time and reference time for time interval measurements

    VKTM acts as a time publisher for an Oracle instance. VKTM publishes two sets of time: a wall clock time using a seconds interval and a higher resolution time (which is not wall clock time) for interval measurements. The VKTM timer service centralizes time tracking and offloads multiple timer calls from other clients.

    Database and ASM instances

    VMB0

    Volume Membership Process

    Maintains cluster membership on behalf of the ASM volume driver

    This process membership in the cluster as an I/O-capable client on behalf of the ASM volume driver.

    ASM instance

    Vnnn

    ASM Volume I/O Slave Process

    Initializes ASM volume contents during creation

    This process is responsible for initializing the ASM volume during creation.

    ASM instance

    Wnnn

    Space Management Slave Process

    Performs various background space management tasks, including proactive space allocation and space reclamation

    Wnnn processes are slave processes dynamically spawned by SMCO to perform space management tasks in the background. These tasks include preallocating space into locally managed tablespace and SecureFiles segments based on space usage growth analysis, and reclaiming space from dropped segments. At most 10 Wnnn slaves can run on one database instance. After being started started, the slave acts as an autonomous agent. After it finishes task execution, it automatically picks up another task from the queue. The process terminates itself after being idle for a long time.

    Database instance

    XDMG

    Exadata Automation Manager

    Initiates automation tasks involved in managing Exadata storage

    XDMG monitors all configured Exadata cells for state changes, such as a bad disk getting replaced, and performs the required tasks for such events. Its primary tasks are to watch for inaccessible disks and cells and when they become accessible again, and to initiate the ASM ONLINE operation. The ONLINE operation is handled by XDWK.

    ASM instance, Exadata

    XDWK

    Exadata Automation Manager

    Performs automation tasks requested by XDMG

    XDWK gets started when asynchronous actions such as ONLINE, DROP, and ADD an ASM disk are requested by XDMG. After a 5 minute period of inactivity, this process will shut itself down.

    ASM instance, Exadata

    Xnnn

    ASM Disk Expel Slave Process

    Performs ASM post-rebalance activities

    This process expels dropped disks at the end of an ASM rebalance.

    ASM instance

    Footnote 1 This background process is available starting with Oracle Database 11g Release 2 (11.2.0.2).
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  • 原文地址：https://www.cnblogs.com/lhdz_bj/p/9407757.html
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