Instance Processes

Question 1

LGWR

Answer 1

Required

Writes transaction recovery information from the SGA redo log buffer to online redo log files.

Question 2

PMON

Answer 2

Process Monitor.
Required
Cleans up failed connections and processes. Resets status of active transaction table and removes process ID from list of active processes. Reclaims memory and undoes locks from failed user session.
Wakes up periodically to check whether it is needed, but can be called explicitly. Also restarts some background processes if they are stopped.

Question 3

SMON

Answer 3

System Monitor
Required
Performs instance recovery after crash using online redo log files, cleans temp segments from dictionary-managed tablespaces and coalesces free space in the DB and manages space used for sorting.
If any dead transactions were skipped during instance recovery because of file IO errors, SMON recovers them once files are back online.
Wakes up regularly to check whether needed. Can be called explicitly.

Question 4

LREG

Answer 4

Listener Registration
Required
Registers information about the instance and dispatcher processes with the listener

Question 5

RECO

Answer 5

Recoverer
Required
Feature: Distributed Database
Recovers failed transactions that are distributed across multiple databases when using distributed database feature.

Question 6

CKPT

Answer 6

Checkpoint
Required
Updates data file headers and control file after checkpoint when change is committed to db.
If incremental checkpoint, just updates ctl file.

Question 7

MMON

Answer 7

Memory Monitor
Required
Feature: Automatic Workload Repository
Gathers and analyzes statistics used by Automatic Workload Repository feature.

Question 8

MMNL

Answer 8

Memory Monitor Light
Required
Feature: Active Session History
Gathers and analyzes statistics used by Active Session History feature.

Question 9

VKTM

Answer 9

Virtual Keeper of Time
Required
Provides wall-clock time (updated every second) and reference-time counter.

Question 10

DIAG

Answer 10

Diagnosability
Required
Performs diagnostic dumps

Question 11

DIA0

Answer 11

Diagnosability
Required
Diag process responsible for hang detection and deadlock resolution.

Question 12

ARCn

Answer 12

Archiver n
Copies transaction recovery info from the redo log files to the archive location. There can be up to 30 of these archival processes.

Question 13

RVWR

Answer 13

Recovery Writer
Feature: Flashback
Writes Flashback data to flashback logs in the FRA.

Question 14

ASMB

Answer 14

ASM Disk
Feature: ASM
ASM service

Question 15

RBAL

Answer 15

ASM Balance
Feature: ASM
Coordinates rebalance activity of disks in an ASM disk group.

Question 16

CJQn

Answer 16

Job Queue Monitor
Feature: Job Scheduling
Assigns jobs to the job queue process (Jnnn) when using Oracle’s job sched feature.

Question 17

Jnnn

Answer 17

Job Queue n
Feature: Job Scheduling
Executes jobs that have been scheduled with job scheduling feature.

Question 18

QMNn

Answer 18

Queue Monitor
Feature: Advanced Queueing
Monitors messages in msg queue when using Advanced Queueing feature.

Question 19

EMNC

Answer 19

Event Monitor

Event management coordination and notification.

Question 20

FBDA

Answer 20

Flashback Data Archive
Feature: Flashback
Archives historical records from table when using Flashback feature

Question 21

Qnnn

Answer 21

Parallel Query Slave
Feature: Parallel Query
Carries out portions of a larger overall query when using Parallel Query feature.

Question 22

Dnnn

Answer 22

Dispatcher
Feature: Shared Server
Assigns db requests to a queue where they are serviced by shared server processes (Snnn) when using Shared Server feature.

Question 23

Snnn

Answer 23

Shared Server
Feature: Shared Server
Process shared among several users when using Shared Server feature.

Question 24

MMAN

Answer 24

Memory Manager
Feature: Automatic Shared Memory
Manages sizes of each SGA component when using Automatic Shared Memory.

Question 25

RVWR

Answer 25

Recovery Writer
Feature: Flashback
Writes recovery info to disk when using Flashback.

Question 26

SMCO

Answer 26

Space Management Coordinator

Coordinates various space management tasks. Worker processes identified as “Wnnn”.

Question 27

DBWn

Answer 27

DBWn
Database Writer
Required
Writes dirty buffers to data files. Up to 100 processes for busy systems. 
DBW0-9, a-z, BW36-99.