Instance level processes

The following background processes will start as soon as the DB2 UDB server is 

started with the 

db2start

 command.

DB2 daemon spawner (db2gds): 

This is a global daemon processor started for each instance. This process 

starts all the EDUs as UNIX processes.

DB2 system controller (db2sysc

): 

This is the system controller processor. Without this process the instance 

cannot function properly.

DB2 watchdog (db2wdog)

:

This process is required only in UNIX platforms. It is the parent process for all 

other processes.

DB2 format log (db2fmtlg)

: 

Pre allocates log files in the log path when the LOGRETAIN database 

configuration parameter is enabled, and the USEREXIT is disabled. 

DB2 system logger (db2syslog)

: 

This is the system logger process responsible for the writing operating system 

error log.

Database level processes

The following background processes are started when a connection activates the 

database:

DB2 log reader (db2loggr): 

This process reads the log files during transaction rollback, restart recovery, 

and roll forward operations.

DB2 log writer (db2logw): 

This is the log writer process that flushes the database log from the log buffer 

to the transaction log files on disk.

DB2 page cleaner (db2pclnr): 

Asynchronous process to make room in the buffer pool by writing changed 

pages to disk, before prefetchers read pages on disk storage and move into 

the buffer pool. 

DB2 prefetcher (db2pfchr): 

This process retrieves data from disk asynchronously, and moves it into the 

buffer pool before the application requests the data. 

 Chapter 1. Introduction 

9