Oracle Background Processes
Required Background Processes
- *DBWn or BWnn - *CKPT - *LGWR - *PMON - *SMON - LREG - RECO - MMON - MMNL - VKTM - DIAG - DIA0
Optional Background Processes
- ARCn - RVWR - ASMB - RBAL - CJQn - Jnnn - QMNn - EMNC - FBDA - Qnnn - Dnnn - Snnn - MMAN - RVWR - CTWR - SMCO
RBAL
ASM Balance Coordinates rebalance activity of disks in an ASM disk group. - Optional
ASMB
ASM Disk Present on databases using Automatic Storage Management disks. - Optional
ARCn
Archiver Copies the transaction recovery information from the redo log files to the archive location. Nearly all production databases use this optional process. You can have up to 30 archival processes (ARC0-ARC9, ARCa-ARCt). - Optional
CTWR
Change Tracking Writer Keeps track of which database blocks have changed when Oracle's incremental Recovery Manager feature is used. - Optional
CKPT
Checkpoint Updates the data file headers following a checkpoint event. - Required
DBWn or BWnn
Database Writer Writes/records modified database blocks from the SGA's database buffer cache to the data files on disk. - Required
DIA0
Diagnosability Diagnostic process responsible for hang detection and deadlock resolution. - Required
DIAG
Diagnosability Performs diagnostic dumps. - Required
Dnnn
Dispatcher Assigns user's database requests to a queue where they are then serviced by shared server processes when Oracle's - Optional
EMNC
Event Monitor Process responsible for event-management coordination and notification. - Optional
FBDA
Flashback Data Archive Archives historical records from a table when the flashback data archive feature is used. - Optional
Jnnn
Job Queue Executes database jobs that have been scheduled using Oracle's job-scheduling feature. - Optional
CJQn
Job Queue Monitor Assigns jobs to the job queue processes when using Oracle's job scheduling feature. - Optional
LREG
Listener Registration Registers information about the database instance and dispatcher processes with the listener. - Required
LGWR
Log Writer Writes transaction recovery information from the SGA's redo log buffer to the online redo log files on disk. - Required
MMAN
Memory Manager Manages the size of each individual SGA component when Oracle's Automatic Shared Memory Management feature is used. - Optional
MMON
Memory Monitor Gathers and analyzes statistics used by the Automatic Workload Repository feature. - Required
MMNL
Memory Monitor Light Gathers and analyzes statistics used by the Active Session History feature. - Required
Qnnn
Parallel Query Slave Carries out portions of a larger overall query when Oracle's Parallel Query feature is used. - Optional
Oracle Background Processes
Performs a specific job in helping to manage an instance - Started by default when the instance starts. - May (not) be used, depending on the features that are being used in the database - Required or Optional Instance terminates abruptly if terminated or error causes shut down any of the processes - Except RECO, DIA0, DIAG (auto restarted if dies/terminated) Parameter: V$BGPROCESS
PMON
Process Monitor Cleans up failed user database connections. - Required
QMNn
Queue Monitor Monitors the messages in the message queue when Oracle's Advanced Queuing feature is used. - Optional
RECO
Recoverer Recovers failed transactions that are distributed across multiple databases when using Oracle's distributed database feature. - Required
RVWR
Recovery Writer Writes flashback data to flashback database logs in the fast recovery area. - Writes recovery information to disk when Oracle's Flashback Database feature is used. - Optional
Snnn
Shared Server Server processes that are shared among several users when Oracle's Shared Server feature is used. - Optional
SMCO
Space Management Coordinator Coordinates various space management tasks. Worker processes are identified with Wnnn. - Optional
SMON
System (Select) Monitor Performs instance recovery following an instance crash, coalesces free space in the database, and manages space used for sorting. - Required
VKTM
Virtual Keeper of Time Responsible for providing a wall-clock time (updated every second) and reference-time counter. - Required