Venzi's Tech-Blog

4 December 2013

Oracle 12c background processes

Filed under: Oracle — Venzi @ 19:48

Here is yet another Oracle 12c post to add to all those out there and this one starts with a question: How many background processes exist in an Oracle DB environment to date? Just take a moment and take a guess, if you haven’t already seen the bold number coming up. The answer is: 108! That is with all the available bells and whistles turned on but it gives you an idea of how much engineering has gone into the Oracle Database over all those 30+ years. In Oracle 12c there is a total of 19 new background processes meaning that if you are running in an 11gR2 environment you will only have 92. Wait, 92? 108 – 19 = 89 and not 92. Those numbers don’t add up so what happened? It is one of those questions I get these days when talking about 12c. Although you can’t change it anyway people want to know what has changed between the versions and I guess: Fair enough. So there you have it, the reason for this post: To share my little research and perhaps answer the same question from one or two people out there before it reaches me via other channels. Or worst case, a link that I can copy/paste rather than having to type this all over again.

Right, so as I’ve mentioned you have a total of 108 background processes in Oracle 12c. You can find the entire list at the bottom of this post or you can have a look at the documentation (always recommended! There are far too many people out there that don’t even bother looking at the documentation anymore).

So, which ones are brand new in 12c:

Name Expanded Name Short Description Long Description External Properties
AQPC AQ Process Coordinator Per instance AQ global coordinator AQPC is responsible for performing administrative tasks for AQ Master Class Processes including commands like starting, stopping, and other administrative tasks. This process is automatically started on instance startup. Database instances Advanced Queueing
ARSn ASM Recovery Slave Process Recovers ASM transactional operations The ASM RBAL background process coordinates and spawns one or more of these slave processes to recover aborted ASM transactional operations. These processes run only in the Oracle ASM instance.Possible processes are ARS0-ARS9. Oracle ASM instances
BWnn Database Writer Process Writes modified blocks from the database buffer cache to the data files See the Long Description for the DBWn process in this table for more information about the BWnn process. Database instances
FENC Fence Monitor Process Processes fence requests for RDBMS instances which are using Oracle ASM instances CSS monitors RDBMS instances which are connected to the Oracle ASM instance and constantly doing I/Os. When the RDBMS instance terminates due to a failure, all the outstanding I/O’s from the RDBMS instance should be drained and any new I/O’s rejected. FENC receives and processes the fence request from CSSD. Oracle ASM instances
IPC0 IPC Service Background Process Common background server for basic messaging and RDMA primitives based on IPC (Inter-process communication) methods. IPC0 handles very high rates of incoming connect requests, as well as, completing reconfigurations to support basic messaging and RDMA primitives over several transports such as UDP, RDS, InfiniBand and RC. Oracle RAC
LDDn Global Enqueue Service Daemon Helper Slave Helps the LMDn processes with various tasks LDDn processes are slave processes spawned on demand by LMDn processes. They are spawned to help the dedicated LMDn processes with various tasks when certain workloads start creating performance bottlenecks. These slave processes are transient as they are started on demand and they can be shutdown when no longer needed. There can be up to 36 of these slave processes (LDD0-LDDz). Database instances, Oracle ASM instances, Oracle RAC
LGnn Log Writer Worker Writes redo log On multiprocessor systems, LGWR creates worker processes to improve the performance of writing to the redo log. LGWR workers are not used when there is a SYNC standby destination. Possible processes include LG00-LG99. Database instances
LREG Listener Registration Process Registers the instance with the listeners LREG notifies the listeners about instances, services, handlers, and endpoint. Database instances, Oracle ASM instances, Oracle RAC
OFSD Oracle File Server Background Process Serves file system requests submitted to an Oracle instance This background process listens for new file system requests, both management (like mount, unmount, and export) and I/O requests, and executes them using Oracle threads. Database instances, Oracle RAC
QMnn AQ Master Class Process Per instance per AQ Master Class Process Each of this type of process represents a single class of work item such as AQ notification, queue monitors, and cross process. Database instances Advanced Queueing
RM RAT Masking Slave Process Extracts and masks bind values from workloads like SQL tuning sets and DB Replay capture files This background process is used with Data Masking and Real Application Testing. Database instances
RMON Rolling Migration Monitor Process Manages the rolling migration procedure for an Oracle ASM cluster The RMON process is spawned on demand to run the protocol for transitioning an ASM cluster in and out of rolling migration mode. Oracle ASM instance, Oracle RAC
RPOP Instant Recovery Repopulation Daemon Responsible for re-creating and/or repopulating data files from snapshot files and backup files The RPOP process is responsible for re-creating and repopulating data files from snapshots files. It works with the instant recovery feature to ensure immediate data file access. The local instance has immediate access to the remote snapshot file’s data, while repopulation of the recovered primary data files happens concurrently. Any changes in the data are managed between the instance’s DBW processes and RPOP to ensure the latest copy of the data is returned to the user. Database instances
SAnn SGA Allocator Allocates SGA A small fraction of SGA is allocated during instance startup. The SAnn process allocates the rest of SGA in small chunks. The process exits upon completion of SGA allocation.The possible processes are SA00 – SAzz. Database instances
SCCn ASM Disk Scrubbing Slave Check Process Performs Oracle ASM disk scrubbing check operation SCCn acts as a slave process for SCRB and performs the checking operations. The possible processes are SCC0-SCC9. Oracle ASM instances
SCRB ASM Disk Scrubbing Master Process Coordinates Oracle ASM disk scrubbing operations SCRB runs in an Oracle ASM instance and coordinates Oracle ASM disk scrubbing operations. Oracle ASM instances
SCRn ASM Disk Scrubbing Slave Repair Process Performs Oracle ASM disk scrubbing repair operation SCRn acts as a slave process for SCRB and performs the repairing operations. The possible processes are SCR0-SCR9. Oracle ASM instances
SCVn ASM Disk Scrubbing Slave Verify Process Performs Oracle ASM disk scrubbing verify operation SCVn acts as a slave process for SCRB and performs the verifying operations. The possible processes are SCV0-SCV9. Oracle ASM instances
VUBG Volume drive Umbilicus Background Relays messages between Oracle ASM instance and Oracle ASM Proxy instance that is used by ADVM (for ACFS) Oracle ASM instances, Oracle ASM Proxy instances

But that is not all. One has actually been renamed all together and two have been enabled for multi-processing indicated by the “n” at the back of the name in the list below:

Name (12c) Previous name (11gR2) Expanded Name Short Description Long Description External Properties
LCKn LCK0 Lock Process Manages global enqueue requests and cross-instance broadcasts The process handles all requests for resources other than data blocks. For examples, LCKn manages library and row cache requests. Possible processes are LCK0 and LCK1. Database instances, Oracle ASM instances, Oracle RAC
LMDn LMD0 Global Enqueue Service Daemon Process Manages incoming remote resource requests from other instances LMDn processes enqueue resources managed under Global Enqueue Service. In particular, they process incoming enqueue request messages and control access to global enqueues. They also perform distributed deadlock detections. There can be up to 36 of these processes (LMD0-LMDz). Database instances, Oracle ASM instances, Oracle RAC
TTnn NSAn Redo Transport Slave Process Ships redo from current online and standby redo logs to remote standby destinations configured for ASYNC transport TTnn can run as multiple processes, where nn is 00 to ZZ.See Also: Oracle Data Guard Concepts and Administration Database instances, Data Guard

And last but not least, three have been made obsolete in 12c:

Name Expanded Name Short Description Long Description External Properties
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
FDnn Oracle ASM Stale FD Cleanup Slave Process Cleans up Oracle ASM stale FDs on foreground processes This process cleans up Oracle ASM stale FDs on foreground processes if an Oracle ASM disk is globally closed. Database and ASM instances
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

The full list of background processes in 12c to date:

Name Expanded Name Short Description Long Description 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 BMRn terminate after being idle for a long time. Database instances
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. Oracle ASM instances, 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 instances, Oracle RAC
APnn Database 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.For more information about the coordinator process, see V$STREAMS_APPLY_COORDINATOR for Oracle Streams, V$XSTREAM_APPLY_COORDINATOR for XStream, and V$GG_APPLY_COORDINATOR for Oracle GoldenGate. Database instances, Logical Standby, Streams Apply, XStream Inbound servers, XStream Outbound servers, GoldenGate Integrated Replicat
AQPC AQ Process Coordinator Per instance AQ global coordinator AQPC is responsible for performing administrative tasks for AQ Master Class Processes including commands like starting, stopping, and other administrative tasks. This process is automatically started on instance startup. Database instances Advanced Queueing
ARBn ASM Rebalance Process Rebalances data extents within an ASM disk group Possible processes are ARB0-ARB9 and ARBA. Oracle ASM instances
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. Database instances
ARSn ASM Recovery Slave Process Recovers ASM transactional operations The ASM RBAL background process coordinates and spawns one or more of these slave processes to recover aborted ASM transactional operations. These processes run only in the Oracle ASM instance.Possible processes are ARS0-ARS9. Oracle ASM instances
ASMB ASM Background Process Communicates with the ASM instance, managing storage and providing statistics ASMB runs in Oracle ASM instances when the ASMCMD cp command runs or when the database instance first starts if the server parameter file is stored in Oracle ASM. ASMB also runs with Oracle Cluster Registry on Oracle ASM. Database instances, Oracle ASM instances
ASnn Database Apply Reader 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, V$XSTREAM_APPLY_READER, and V$GG_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$STREAMS_APPLY_SERVER for information about the apply server background process. For XStream Inbound servers, query V$XSTREAM_APPLY_SERVER. For GoldenGate Integrated Replicat, query V$GG_APPLY_SERVER.The coordinator process name is ASnn, where nn can include letters and numbers. Database instances, XStream Outbound servers, XStream Inbound servers, GoldenGate Integrated Replicat
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. Database instances
Bnnn ASM Blocking Slave Process for GMON Performs maintenance actions on Oracle 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 Oracle 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. Oracle ASM instances
BWnn Database Writer Process Writes modified blocks from the database buffer cache to the data files See the Long Description for the DBWn process in this table for more information about the BWnn process. Database instances
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. Database instances
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.CKPT checks every three seconds to see whether the amount of memory exceeds the value of the PGA_AGGREGATE_LIMIT initialization parameter, and if so, takes the action described in “PGA_AGGREGATE_LIMIT”. Database instances, Oracle ASM instances
CPnn Database 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_CAPTURE, V$XSTREAM_CAPTURE, and V$GOLDENGATE_CAPTURE view for information about this background process. Database instances, XStream Outbound Servers, 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 instances, 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. Database instances
CXnn Streams Propagation Sender Process Sends LCRs to a propagation receiver The propagation sender process name is CXnn, 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 instances, XStream Outbound Server, Oracle Streams
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. Database instances
DBWn Database Writer Process Writes modified blocks from the database buffer cache to the data files The primary responsibility of the Database Writer Process is to write data blocks to disk. It also handles checkpoints, file open synchronization, and logging of Block Written records.In many cases the blocks that the Database Writer Process writes are scattered throughout the disk. Thus, the writes tend to be slower than the sequential writes performed by LGWR. The Database Writer Process 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 Database Writer Processes. There can be 1 to 100 Database Writer Processes. The names of the first 36 Database Writer Processes are DBW0-DBW9 and DBWa-DBWz. The names of the 37th through 100th Database Writer Processes are BW36-BW99. The database selects an appropriate default setting for the DB_WRITER_PROCESSES parameter or adjusts a user-specified setting based on the number of CPUs and processor groups. Database instances
DIA0 Diagnostic Process Detects and resolves hangs and deadlocks Database instances, Oracle ASM 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. Database instances, Oracle ASM 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 instances, 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. Database instances, 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. Database instances, shared servers
DSKM Slave Diskmon Process Acts as the conduit between the database, Oracle 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. Oracle ASM instances, 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 instances
EMNC EMON Coordinator Process Coordinates database event management and notifications EMNC is a master background process that coordinates event management and notification activity in the database, including Streams Event Notifications, Continuous Query Notifications, and Fast Application Notifications. Database 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 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. Database instances
FENC Fence Monitor Process Processes fence requests for RDBMS instances which are using Oracle ASM instances CSS monitors RDBMS instances which are connected to the Oracle ASM instance and constantly doing I/Os. When the RDBMS instance terminates due to a failure, all the outstanding I/O’s from the RDBMS instance should be drained and any new I/O’s rejected. FENC receives and processes the fence request from CSSD. Oracle 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 instances, Oracle 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 instances, Data Guard
GCRn 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 instances, Oracle ASM instances, Oracle RAC
GEN0 General Task Execution Process Performs required tasks including SQL and DML Database instances, Oracle ASM instances, Oracle ASM Proxy instances
GMON ASM Disk Group Monitor Process Monitors all mounted Oracle ASM disk groups GMON monitors all the disk groups mounted in an Oracle 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. Oracle ASM instances
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 processes disabled, an error is returned. Database instances, 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 instances
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 instances, Data Guard
IPC0 IPC Service Background Process Common background server for basic messaging and RDMA primitives based on IPC (Inter-process communication) methods. IPC0 handles very high rates of incoming connect requests, as well as, completing reconfigurations to support basic messaging and RDMA primitives over several transports such as UDP, RDS, InfiniBand and RC. Oracle RAC
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 instances
LCKn Lock Process Manages global enqueue requests and cross-instance broadcasts The process handles all requests for resources other than data blocks. For examples, LCKn manages library and row cache requests. Possible processes are LCK0 and LCK1. Database instances, Oracle ASM instances, Oracle RAC
LDDn Global Enqueue Service Daemon Helper Slave Helps the LMDn processes with various tasks LDDn processes are slave processes spawned on demand by LMDn processes. They are spawned to help the dedicated LMDn processes with various tasks when certain workloads start creating performance bottlenecks. These slave processes are transient as they are started on demand and they can be shutdown when no longer needed. There can be up to 36 of these slave processes (LDD0-LDDz). Database instances, Oracle ASM instances, Oracle RAC
LGnn Log Writer Worker Writes redo log On multiprocessor systems, LGWR creates worker processes to improve the performance of writing to the redo log. LGWR workers are not used when there is a SYNC standby destination. Possible processes include LG00-LG99. Database instances
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. Database instances, Oracle ASM instances
LMDn Global Enqueue Service Daemon Process Manages incoming remote resource requests from other instances LMDn processes enqueue resources managed under Global Enqueue Service. In particular, they process incoming enqueue request messages and control access to global enqueues. They also perform distributed deadlock detections. There can be up to 36 of these processes (LMD0-LMDz). Database instances, Oracle 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 instances, Oracle 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. Database instances, Oracle 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. Database instances, Oracle ASM instances, Oracle RAC
LREG Listener Registration Process Registers the instance with the listeners LREG notifies the listeners about instances, services, handlers, and endpoint. Database instances, Oracle 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 run-time parameter changes for the SQL Apply product as a whole. Database instances, 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 because of switchover or failover. The dictionary is necessary for logical standby databases to interpret the redo of the new primary database. Database instances, 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 instances, 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. Database instances, 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 Oracle ASM instance. If required, MARK can also be started on demand when disks go offline in the Oracle ASM redundancy disk group. Database instances, Oracle ASM instances
MMAN Memory Manager Process Serves as the instance memory manager This process performs the resizing of memory components on the instance. Database instances, Oracle 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 instances, Oracle 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 instances, Oracle 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 instances, Oracle 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. Database instances, 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 or a database capture. There may be more than one such group, for example, multiple capture processes configured for either local or downstream capture in a database. Database instances, Logical Standby, Oracle Streams, XStream Outbound servers, Oracle GoldenGate
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. Database instances, Database Resident Connection Pooling
NSSn Network Server SYNC Process Transfers redo from current online redo logs to remote standby destinations configured for SYNC transport NSSn can run as multiple processes, where n is 1-9 or A. Database instances, 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 instances, Data Guard
OCFn ASM CF Connection Pool Process Maintains a connection to the Oracle ASM instance for metadata operations Database instances, Oracle ASM instances
OFSD Oracle File Server Background Process Serves file system requests submitted to an Oracle instance This background process listens for new file system requests, both management (like mount, unmount, and export) and I/O requests, and executes them using Oracle threads. Database instances, Oracle RAC
Onnn ASM Connection Pool Process Maintains a connection to the Oracle ASM instance for metadata operations Onnn slave processes are spawned on demand. These processes communicate with the Oracle ASM instance. Database instances, Oracle 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 instances, Oracle 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

Database instances, Oracle ASM instances, Oracle ASM Proxy 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 perform 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 instances, Oracle 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 instances
PSP0 Process Spawner Process Spawns Oracle background processes after initial instance startup Database instances, Oracle ASM instances
QMNC Non-sharded queue master process Monitors AQ QMNC is the non-sharded queue master process 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 instances Advanced Queueing
QMnn AQ Master Class Process Per instance per AQ Master Class Process Each of this type of process represents a single class of work item such as AQ notification, queue monitors, and cross process. Database instances Advanced Queueing
Qnnn AQ Server Class Process Per AQ Master Class server process Each server class process acts on behalf of an AQ master class process. This relationship is maintained until the master requires services of a particular service process. Once released, the server class processes are moved to a free server pool. Database instances Advanced Queueing
RBAL ASM Rebalance Master Process Coordinates rebalance activity In an Oracle ASM instance, it coordinates rebalance activity for disk groups. In a database instances, it manages Oracle ASM disk groups. Database instances, Oracle 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 instances, 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. Database instances
RM RAT Masking Slave Process Extracts and masks bind values from workloads like SQL tuning sets and DB Replay capture files This background process is used with Data Masking and Real Application Testing. Database instances
RMON Rolling Migration Monitor Process Manages the rolling migration procedure for an Oracle ASM cluster The RMON process is spawned on demand to run the protocol for transitioning an ASM cluster in and out of rolling migration mode. Oracle ASM instance, Oracle RAC
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. Database instances, Oracle RAC
Rnnn ASM Block Remap Slave Process Remaps a block with a read error A database instance reading from an Oracle ASM disk group can encounter an error during a read. If possible, Oracle ASM asynchronously schedules a Rnnn slave process to remap this bad block from a mirror copy. Oracle ASM instances
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 instances
RPOP Instant Recovery Repopulation Daemon Responsible for re-creating and/or repopulating data files from snapshot files and backup files The RPOP process is responsible for re-creating and repopulating data files from snapshots files. It works with the instant recovery feature to ensure immediate data file access. The local instance has immediate access to the remote snapshot file’s data, while repopulation of the recovered primary data files happens concurrently. Any changes in the data are managed between the instance’s DBW processes and RPOP to ensure the latest copy of the data is returned to the user. Database instances
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 instances, 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 instances, Oracle RAC
RVWR Recovery Writer Process Writes flashback data to the flashback logs in the fast 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 instances, Flashback Database
SAnn SGA Allocator Allocates SGA A small fraction of SGA is allocated during instance startup. The SAnn process allocates the rest of SGA in small chunks. The process exits upon completion of SGA allocation.The possible processes are SA00 – SAzz. Database instances
SCCn ASM Disk Scrubbing Slave Check Process Performs Oracle ASM disk scrubbing check operation SCCn acts as a slave process for SCRB and performs the checking operations. The possible processes are SCC0-SCC9. Oracle ASM instances
SCRB ASM Disk Scrubbing Master Process Coordinates Oracle ASM disk scrubbing operations SCRB runs in an Oracle ASM instance and coordinates Oracle ASM disk scrubbing operations. Oracle ASM instances
SCRn ASM Disk Scrubbing Slave Repair Process Performs Oracle ASM disk scrubbing repair operation SCRn acts as a slave process for SCRB and performs the repairing operations. The possible processes are SCR0-SCR9. Oracle ASM instances
SCVn ASM Disk Scrubbing Slave Verify Process Performs Oracle ASM disk scrubbing verify operation SCVn acts as a slave process for SCRB and performs the verifying operations. The possible processes are SCV0-SCV9. Oracle ASM instances
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 instances
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.

Database instances
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.
TEMn ASM disk Test Error Emulation Process Emulates I/O errors on Oracle ASM disks through named events I/O errors can be emulated on Oracle 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. Oracle ASM instances
TTnn Redo Transport Slave Process Ships redo from current online and standby redo logs to remote standby destinations configured for ASYNC transport TTnn can run as multiple processes, where nn is 00 to ZZ. Database instances, Data Guard
VBGn Volume Background Process Communicates between the Oracle 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 Oracle ASM instance.VBGn can run as multiple processes, where n is 0-9. Oracle ASM instances, Oracle ASM Proxy instances
VDBG Volume Driver Process Forwards Oracle 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. Oracle ASM instances, Oracle ASM Proxy instances
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 instances
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 instances, Oracle ASM instances
VMB0 Volume Membership Process Maintains cluster membership on behalf of the Oracle ASM volume driver This process membership in the cluster as an I/O-capable client on behalf of the Oracle ASM volume driver. Oracle ASM instances, Oracle ASM Proxy instances
VUBG Volume drive Umbilicus Background Relays messages between Oracle ASM instance and Oracle ASM Proxy instance that is used by ADVM (for ACFS) Oracle ASM instances, Oracle ASM Proxy instances
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, 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 instances
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. Oracle ASM instances, Exadata
XDWK Exadata Automation Manager Performs automation tasks requested by XDMG XDWK gets started when asynchronous actions such as ONLINE, DROP, and ADD an Oracle ASM disk are requested by XDMG. After a 5 minute period of inactivity, this process will shut itself down. Oracle ASM instances, Exadata
Xnnn ASM Disk Expel Slave Process Performs Oracle ASM post-rebalance activities This process expels dropped disks after an Oracle ASM rebalance. Oracle ASM instances

Leave a Comment »

No comments yet.

RSS feed for comments on this post. TrackBack URI

Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out / Change )

Twitter picture

You are commenting using your Twitter account. Log Out / Change )

Facebook photo

You are commenting using your Facebook account. Log Out / Change )

Google+ photo

You are commenting using your Google+ account. Log Out / Change )

Connecting to %s

The Rubric Theme. Blog at WordPress.com.

Follow

Get every new post delivered to your Inbox.

%d bloggers like this: