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