Background Processes in Oracle Database 12c

General
Acronym	Process Name	Description	Required for basic DB operation	Started by default	New in this release
ABMR	Auto BMR Background Process	Coordinates execution of tasks such as filtering duplicate block media recovery requests and performing flood control.	No	No	No
APnn	Logical Standby / Streams Apply Process Coordinator Process	Obtains transactions from the reader server and passes them to apply servers	No	No	No
ARC 0..t	Archiver Process (30 possible)	Copies the redo log files to archival storage when they are full or an online redo log switch occurs	No	No	No
BMRn	Automatic Block Media Recovery Slave Pool Process	Fetches blocks from a real-time readable standby database	No	No	No
BW nn	Database Writer Process (20 possible)	Writes modified blocks from the database buffer cache to the data files. The names of the 37th through 100th Database Writer Processes are BW36-BW99. See DBWn for more information on these processes.	Yes	Yes	Yes
CJQ0	Job Queue Coordinator Process	Spawns slave processes (Jnnn) to execute jobs in the queue.	No	Yes	No
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	Yes	Yes	No
CPnn	Database Capture Process	Captures database changes from the redo log by using the infrastructure of LogMiner.	No	No	No
CSnn	Streams Propagation Sender Process	Sends LCRs to a propagation receiver.	No	No	No
CSnn	I/O Calibration Process	Issues I/Os to storage as part of storage calibration. There is one slave process per CPU on each node of the database.	Yes	Yes	No
CTWR	Change Tracking Writer Process	Tracks changed data blocks as part of the Recovery Manager block change tracking feature	No	No	No
DBRM	Database Resource Manager Process	Sets resource plans and performs other Resource Manager tasks.	No	Yes	No
DBW 0..j	Database Writer Process	Writes modified blocks from the database buffer cache to the data files. 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.	Yes	Yes	No
DIA0	Diagnostic Process 0 (although 10 possible, only 0 is currently used)	Responsible for hang detection and deadlock resolution. Triggers DIAG to perform diagnostic tasks.	Yes	Yes	No
DIAG	Diagnostic Capture Process	Performs diagnostic dumps and executes global oradebug commands.	Yes	Yes	No
DMnn	Data Pump Master Process	Coordinates the Data Pump job tasks performed by Data Pump worker processes and handles client interactions.	No	No	No
Dnnn	Dispatcher Process	In a Shared Server configuration, dispatchers place connection requests in a connection request queue.	No	Yes	No
DWnn	Data Pump Worker Process	Performs Data Pump tasks as assigned by the Data Pump Master Process.	No	No	No
EMNC	EMON Coordinator Process	Coordinates the event management and notification activity in the database, including Streams Event Notifications, Continuous Query Notifications, and Fast Application Notifications. Spawns Ennn processes.	No	No	No
Ennn	EMON Slave Process	Performs database event management and notifications.	No	No	No
FBDA	Flashback Data Archiver Process	Archives historical rows for tracked tables into flashback data archives and manages archive space, organization, and retention	No	No	No
FMON	File Mapping Monitor Process	Spawns FMPUTL, an external non-Oracle Database process that communicates with the mapping libraries provided by storage vendors. Responsible for managing the mapping information.	No	No	No
GEN0	General Task Execution Process	Performs required tasks including SQL and DML.	Yes	Yes	No
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.	No	No	No
Jnnn	Job Queue Slave Processes	Processes jobs in the queue. Spawned by CJQ0.	No	Yes	No
LGn	Log Writer Slave	On multiprocessor systems, LGWR creates slave processes to improve the performance of writing to the redo log. LGWR slaves are not used when there is a SYNC standby destination.	No	No	Yes
LGWR	Log Writer Process	Writes the log buffer out to the redo logs.	Yes	Yes	No
Lnnn	Pooled Server Process	Handles client requests in Database Resident Connection Pooling.	No	No	No
LREG	Listener Registration Process	LREG notifies the listeners about instances, services, handlers, and endpoint.	Yes	Yes	Yes
MMAN	Memory Manager Process	Serves as the SGA Memory Broker and coordinates the sizing of the memory components.	No	Yes	No
MMNL	Manageability Monitor Lite Process	Performs frequent and lightweight manageability-related tasks, such as session history capture and metrics computation.	No	Yes	No
MMON	Manageability Monitor Process	Collects statistics for the Automatic Workload Repository.	No	Yes	No
Mnnn	MMON Slave Process	Performs manageability tasks on behalf of MMON.	No	No	No
MSnn	LogMiner Worker Process	Reads redo log files and translates and assembles into transactions.	No	No	No
Nnnn	Connection Broker Process	Monitors idle connections and hands off active connections in Database Resident Connection Pooling	No	No	No
OFSD	Oracle File Server Background Process	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.	Yes	Yes	No
PMON	Process Monitor	Recovers failed process resources. If Shared Server architecture is used, PMON monitors and restarts any failed dispatcher or server processes.	Yes	Yes	No
Pnnn	Parallel Query Slave Process	Started and stopped as needed to participate in parallel query operations.	No	No	No
PRnn	Parallel Recovery Process	Performs tasks assigned by the coordinator process performing parallel recovery	No	No	No
PSP0	Process Spawner Process	Starts and stops Oracle processes. Reduces workload of RBAL by starting / stopping ASM rebalance slaves.	No	Yes	No
RCBG	Result Cache Background Process	Supports SQL query and PL/SQL function result caches.	No	No	No
RECO	Recoverer Process	Resolves failures involving distributed transactions.	No	Yes	No
RM	RAT Masking Slave Process	This background process is used with Data Masking and Real Application Testing.	No	Yes	Yes
RPnn	Capture Processing Worker Process	Processes a set of workload capture files.	No	No	No
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.	No	No	Yes
RVWR	Recovery Writer Process	Writes flashback data to flashback database logs in the flash recovery area.	No	No	No
SAnn	SG Allocator	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.	No	Yes	Yes
SMCO	Space Management Coordinator Process	Coordinates the execution of various space management related tasks, such as proactive space allocation and space reclamation.	No	Yes	No
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	Yes	Yes	No
Snnn	Shared Server Process	In a Shared Server configuration, shared servers check a connection request queue (populated by dispatchers) and services the connection requests.	No	Yes	No
VKRM	Virtual Scheduler for Resource Manager Process	Serves as centralized scheduler for Resource Manager activity.	No	Yes	No
VKTM	Virtual Keeper of Time Process	Responsible for providing a wall-clock time (updated every second) and reference-time counter (updated every 20ms and available only when running at elevated priority).	Yes	Yes	No
Wnnn	Space Management Slave Process	These are slave processes spawned by SMCO to execute space management tasks.	No	Yes	No

Exadata
Acronym	Process Name	Description	Required for basic DB operation	Started by default	New in this release
DSKM	Slave Diskmon Process	Acts as conduit between RDBMS and ASM instances and the Master Diskmon daemon to communicate I/O Fencing information, I/O Resource Manager Plans, and Transaction Commit Cache information to Exadata storage. If no Exadata storage is used, the slave diskmon process will exit silently after startup of the instance. Only active if Exadata storage is used.	No	No	No
XDMG	Exadata Automation Manager	Initiates automation tasks involved in managing Exadata storage	No	No	No
XDWK	Exadata Automation Worker	Performs automation tasks requested by XDMG	No	No	No

Oracle Real Application Clusters
Acronym	Process Name	Description	Required for basic DB operation	Started by default	New in this release
ACMS	Atomic Control File to Memory Server Process	Coordinates consistent updates to a control file resource with its SGA counterpart on all instances in an Oracle RAC environment	No	No	No
GTX 0..j	Global Transaction Process (20 possible)	Provides transparent support for XA global transactions in an Oracle RAC environment. The database auto tunes the number of these processes based on the workload of XA global transactions.	No	No	No
IPC0	IPC Service Background Process	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.	No	No	Yes
LCKn	Lock Process	Manages the global enqueue requests and the cross-instance broadcast. Handles all requests for resources other than data blocks.	No	No	No
LDDn	Global Enqueue Service Daemon Helper Slave	Helps the LMDn processes with various tasks. LDDn processes are slaves 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.	No	No	Yes
LMDn	Global Enqueue Service Daemon Process	Manages enqueue manager service requests for Global Cache Service enqueues to control access to global enqueues and resources. The LMD process also handles deadlock detection and remote enqueue requests. Remote resource requests are the requests originating from another instance.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).	No	No	No
LMHB	Global Cache / Enqueue Service Heartbeat Monitor	Monitors the heartbeat of LMON, LMD, and LMSn processes.	No	No	No
LMON	Global Enqueue Service Monitor Process	Monitors the entire cluster to manage the global enqueues and the resources. Manages instance and process failures and the associated recovery for the Global Cache Service (GCS) and Global Enqueue Service (GES). In particular, LMON handles the part of recovery associated with global resources. LMON-provided services are also known as cluster group services (CGS).	No	No	No
LMS 0..z	Global Cache Service Process (36 possible)	Handles remote Global Cache Service (GCS) messages. The number of LMS processes varies depending on the amount of messaging traffic among nodes in the cluster.	No	No	No
PING	Interconnect Latency Measurement Process	Assesses the latencies associated with communications for each pair of instances. Every few seconds, the process in one instance (INSTANCE_NUMBER value) sends two messages to each instance (TARGET_INSTANCE value). One message has a size of 500 bytes and the other has a size of 8 KB. The message is received by the PING process on the target instance and is immediately acknowledged. The time for the round-trip is measured and collected.	No	No	No
RMSn	Oracle RAC Management Process	RMSn performs a variety of tasks, including creating resources related to Oracle RAC when new instances are added to a cluster.	No	No	No
RSMN	Remote Slave Monitor Process	Manages background slave process creation and communication on remote instances.	No	No	No

Oracle Data Guard
Acronym	Process Name	Description	Required for basic DB operation	Started by default	New in this release
ASnn	Database Apply Reader or Apply Server	As the Reader Server, computes dependencies between LCRs and assembles messages into transactions. As the Apply Server, applies LCRs to database objects, or passes LCRs to the appropriate apply handlers.	No	No	No
DMON	Data Guard Broker Monitor Process	Starts when Data Guard Broker is started. The server-side component that interacts with the local database and the DMON processes of the other databases to perform the requested function. Also responsible for monitoring the health of the broker configuration and for ensuring that every database has a consistent description of the configuration.	No	No	No
FSFP	Data Guard Broker Fast Start Failover Pinger Process	Observer process integrated in the DGMGRL client-side component. It monitors the DG Broker environment and initiates the failover on detecting a problem with Primary.	No	No	No
INSV	Data Guard Broker Instance Slave Process	Performs Data Guard Broker communication between instances of a RAC database.	No	No	No
LSP0	Logical Standby Coordinator Process	Assigns transactions to different Data Guard appliers and coordinates among them to ensure that dependencies between transactions are honored.	No	No	No
LSP1	Logical Standby Dictionary Build Process	Builds the data dictionary for the Logical Standby.	No	No	No
LSP2	Logical Standby Set Guard Process	Maintains Guard Standby information for the Logical Standby.	No	No	No
MRP0	Managed Standby Recovery Process	Provides transparent support for XA global transactions in RAC	No	No	No
NSSn	Network Server Sync Process	Transfers redo from current online redo logs to remote standby destinations configured for SYNC transport	No	No	No
NSV 0..9	Data Guard Broker NetSlave Process (10 possible)	Performs broker network communications between databases in a Data Guard configuration.	No	No	No
RSM0	Data Guard Broker Worker Server Process	Used by the DMON process to manage and monitor the database.	No	No	No
TMON	Transport Monitor	TMON starts the TMON slave (called the TT processes) and monitors a number of redo transport processes for hangs and death.	No	No	Yes
TTnn	Redo Transport Slave Process	Ships redo from current online and standby redo logs to remote standby destinations configured for ASYNC transport	No	No	Yes

Oracle Advanced Queuing
Acronym	Process Name	Description	Required for basic DB operation	Started by default	New in this release
QMNC	AQ Coordinator Process	Monitors message queues. Spawns Qnnn slave processes.	No	Yes	No
QMnn	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.	No	No	No
Qnnn	AQ Server Class Process	Processes messages in the Streams AQ queue. Spawned by QMNC.	No	Yes	No

Automatic Storage Management
Acronym	Process Name	Description	Required for basic DB operation	Started by default	New in this release
ACFS	ASM Cluster File System CSS Process	Tracks the cluster membership in CSS and informs the file system driver of membership changes.	No	No	No
ARB 0..A	ASM Rebalance Process (11 possible)	Rebalances data extents across the ASM file systems.	No	No	No
ARSn	ASM Recovery Slave Process (10 possible)	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.	No	No	Yes
ASMB	ASM Background Process	Communicates with the ASM instance, managing storage and providing statistics	No	No	No
B00 0..4	ASM Blocking Slave Process for GMON	Performs maintenance actions on ASM disk groups	No	No	No
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.	No	No	Yes
FENC	Fence Monitor Process	Processes fence requests for RDBMS instances which are using Oracle ASM IOServer instances	No	No	Yes
GMON	ASM Disk Group Monitor Process	Maintains disk membership in ASM disk groups.	No	No	No
MARK	Mark AU for Resynchronization Coordinator Process	Marks ASM Allocation Units as stale following a missed write to an offline disk	No	No	No
OCFn	ASM CF Connection Pool Process	Maintains a connection to the ASM instance for metadata operations	No	No	No
Onnn	ASM Connection Pool Process	Maintains a connection to the ASM instance for metadata operations	No	No	No
RBAL	ASM Rebalance Master Process	In an Oracle ASM instance, it coordinates rebalance activity for disk groups. In a database instances, it manages Oracle ASM disk groups.	No	No	No
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.	Yes	No	Yes
Rnnn	ASM Block Remap Slave Process	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.	No	No	No
SCCn	ASM Disk Scrubbing Slave Check Process	SCCn acts as a slave process for SCRB and performs the checking operations.	No	No	Yes
SCRB	ASM Disk Scrubbing Master Process	SCRB runs in an Oracle ASM instance and coordinates Oracle ASM disk scrubbing operations.	No	No	Yes
SCRn	ASM Disk Scrubbing Slave Repair Process	SCRn acts as a slave process for SCRB and performs the repairing operations.	No	No	Yes
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.	No	No	Yes
TEMn	ASM Disk Test Error Emulation Process	Emulates I/O errors on ASM disks through named events.	No	No	No
VBGn	Volume Background Process	Communicates between the ASM instance and the operating system volume driver.	No	No	No
VDBG	Volume Driver Process	Forwards ASM request to perform various volume-related tasks.	No	No	No
VMBO	Volume Membership Process	Maintains cluster membership on behalf of the ASM volume drivers	No	No	No
VUBG	Volume drive Umbilicus Background	Relays messages between Oracle ASM instance and Oracle ASM Proxy instance that is used by ADVM (for ACFS)	No	No	Yes
Xnnn	ASM Disk Expel Slave Process	Performs Oracle ASM post-rebalance activities. This process expels dropped disks at the end of an Oracle ASM rebalance.	No	No	Yes