Oracle background processes

The background processes are part of the SGA.

Each background process is designed to perform a specific taks. They work with each other. Many processes also operate on data files.

There are mandatory and optional processes.

The mandatory background processes are created when a instance is started.

Background processes have v$session.type = BACKGROUND.

            Mandatory

   Qnnn  advanced queueing processes  

   ARCn  The archiver processes archives redo log files (if ARCHIVELOG is enabeled)  

   CKPT  The checkpoint process regularly initiates a checkpoint which uses DBWn to write all dirty blocks back to the datafile (thus synchronizing the datrabase).  ✓

   CJQ0  Coordinator-of-job-queues process: dynamically spawns slave processes for job-queues  

   DBWn  The database writer processes write dirty blocks from the database buffer to datafiles. Number of processes according to init param DB_WRITER_PROCESSES.  ✓

   Dnnn  The dispatcher process, used in a shared server environment  

   DMnn  Data Pump master process   

   DWnn  Data Pump worker processes   

   Dnnn  dispatcher processes: multiplex server-processes on behalf of users  

   DMON  The main Data Guard Broker monitor process  

   FBDA  The Flashback Data Archive Process 

   Jnnn  Job-queue slave processes  

   LCKnnnn (?)  The inter-instance locking process (?) 

   LGWR  The log-writer process writes the redo log buffer from the SGA to the online redo log file.  ✓

   LGnn  Log Writer Worker helper processes (aka «Log Writer Slave» )

LMD0 (?) 

   LNSn  log-write network-server: transmits redo logs in Data Guard environments  

    LMON  The lock manager, found in RAC instances only 

   LREG  The listener registration process  ✓

   LSP0  logical standby coordinator process: controls Data Guard log-application  

   MRP   The media-recovery process applies archived redo log to a standby database.  

   MMAN  The memory-manager process is used for internal database tasks such as Automatic Shared Memory Management (ASMM)  

   MMON  The Manageability-monitor process for automatic problem-detection, self-tuning and statistics-gathering  ✓

   MMNL  The Manageability-monitor light process: gathers and stores Automatic Workload Repository (AWR) data  ✓

    ?      mmon slaves (Mnnnn—M0000, M0001 etc.): background slaves of the MMON process  

   NSVn  netslave processes: Data Guard Broker inter-database communication processes  

   Pnnn  parallel query execution servers  

   PMAN  Process Manager  ✓

   PMON  The process-monitor process frees up resources of failed user processes. Wakes up every 3 seconds.  ✓

   PSP0  process-spawner process: spawns Oracle background processes after initial instance startup[107]  

   QMNC  queue-monitor coordinator process: dynamically spawns queue monitor slaves[108]  

   QMNn  queue-monitor processes (AQ Time Manager?)  

   RECO  The recoverer process finds pending distributed transactions and resolves them.  ✓

   RFS   The remote file-server process runs on a standby database and receives archived redo logs from the primary database.  

   RFS   monitor for Data Guard management: Data Guard Broker Worker process[110]  

   RVWR  The recovery writer process 

   Snnn  The shared server processes is used in a shred server environment to serve client-requests  

SNPnnn   The snapshot process ? 

   SMCO  The space-management coordinator process coordinates space management  

   SMON  The system monitor process performs instance recovery, cleans up after dirty shutdowns and coalesces adjacent free extents into larger free extents. Wakes up every 5 minutes.  ✓

TRWR(?)  Trace file writer (?) 

   TTnn  The Redo Transport Slave Process ships redo from the current online and standby redo logs to the remote standby destinations configured for Asynchronous redo transport 

VKTM     Virtual Keeper of Time. (Apparently, am others?, used in conjunction with oradebug ffbegin and/or oradebug resumeinst. 

WMON(?)  The wakeup monitor process (?) 

Others(?):

AQPC: AQ Process Coord
CLMN: process cleanup
DBRM: DataBase Resource Manager
DIAG: diagnosibility process
DIA0: diagnosibility process 0
FENC: IOServer fence monitor
FMON
GEN0, GEN1: generic0, generic1
M: MMON slave class 1
MZ: MMON slave class 2
PXMN: PX Monitor
SA*: KSM SGA allocator class (KSM = Kernel Service, Memory?, See also x$ksm…)
SVCB: services background monitor
TMON: Transport Monitor
TT*: Redo Transport
VKRM: Virtual sKeduler for Resource Manager
Wnnn: space management slave pool

Slave processes

Slave processes perform work on behalf of other processes.

The slave processes are:

Dnnn
Snnn

		Mandatory
`Qnnn`	advanced queueing processes
`ARCn`	The archiver processes archives redo log files (if `ARCHIVELOG` is enabeled)
`CKPT`	The checkpoint process regularly initiates a checkpoint which uses `DBWn` to write all dirty blocks back to the datafile (thus synchronizing the datrabase).	✓
`CJQ0`	Coordinator-of-job-queues process: dynamically spawns slave processes for job-queues
`DBWn`	The database writer processes write dirty blocks from the database buffer to datafiles. Number of processes according to init param `DB_WRITER_PROCESSES`.	✓
`Dnnn`	The dispatcher process, used in a shared server environment
`DMnn`	Data Pump master process
`DWnn`	Data Pump worker processes
`Dnnn`	dispatcher processes: multiplex server-processes on behalf of users
`DMON`	The main Data Guard Broker monitor process
`FBDA`	The Flashback Data Archive Process
`Jnnn`	Job-queue slave processes
`LCKnnnn` (?)	The inter-instance locking process (?)
`LGWR`	The log-writer process writes the redo log buffer from the SGA to the online redo log file.	✓
`LGnn`	Log Writer Worker helper processes (aka «Log Writer Slave» )
`LMD0` (?)
`LNSn`	log-write network-server: transmits redo logs in Data Guard environments
`LMON`	The lock manager, found in RAC instances only
`LREG`	The listener registration process	✓
`LSP0`	logical standby coordinator process: controls Data Guard log-application
`MRP`	The media-recovery process applies archived redo log to a standby database.
`MMAN`	The memory-manager process is used for internal database tasks such as Automatic Shared Memory Management (ASMM)
`MMON`	The Manageability-monitor process for automatic problem-detection, self-tuning and statistics-gathering	✓
`MMNL`	The Manageability-monitor light process: gathers and stores Automatic Workload Repository (AWR) data	✓
?	mmon slaves (`Mnnnn`—`M0000`, `M0001` etc.): background slaves of the `MMON` process
`NSVn`	netslave processes: Data Guard Broker inter-database communication processes
`Pnnn`	parallel query execution servers
`PMAN`	Process Manager	✓
`PMON`	The process-monitor process frees up resources of failed user processes. Wakes up every 3 seconds.	✓
`PSP0`	process-spawner process: spawns Oracle background processes after initial instance startup[107]
`QMNC`	queue-monitor coordinator process: dynamically spawns queue monitor slaves[108]
`QMNn`	queue-monitor processes (AQ Time Manager?)
`RECO`	The recoverer process finds pending distributed transactions and resolves them.	✓
`RFS`	The remote file-server process runs on a standby database and receives archived redo logs from the primary database.
`RFS`	monitor for Data Guard management: Data Guard Broker Worker process[110]
`RVWR`	The recovery writer process
`Snnn`	The shared server processes is used in a shred server environment to serve client-requests
`SNPnnn`	The snapshot process ?
`SMCO`	The space-management coordinator process coordinates space management
`SMON`	The system monitor process performs instance recovery, cleans up after dirty shutdowns and coalesces adjacent free extents into larger free extents. Wakes up every 5 minutes.	✓
`TRWR`(?)	Trace file writer (?)
`TTnn`	The Redo Transport Slave Process ships redo from the current online and standby redo logs to the remote standby destinations configured for Asynchronous redo transport
`VKTM`	Virtual Keeper of Time. (Apparently, am others?, used in conjunction with `oradebug ffbegin` and/or `oradebug resumeinst`.
`WMON`(?)	The wakeup monitor process (?)

Oracle background processes

Slave processes

See also