System Architecture 2-33

OnLine Daemon Processes

OnLine Daemon Processes
Daemon processes are OnLine user processes that perform system-wide
tasks. Unlike database server processes, a daemon process is not associated
with a corresponding application development tool process.
The OnLine system employs three different types of daemons, which are
listed below.
■tbinit, the master daemon
■tbundo, the undertaker daemon
■tbpgcl, a page-cleaner daemon
Daemon processes are identified in tbstat -u output by aD (daemon) flag or
an F (page cleaner or “flusher”) flag in the fourth flag position of the user
entry.

tbinit Daemon

Thetbinit daemon is spawned by the tbinit process early in the initialization
process. Thetbinit daemon occupies the first entry in the shared-memory
user table, which is represented by the first entry intbstat -u output.
The tbinit daemon is responsible for most of the tasks of disk space and
shared-memory initialization. (Refer topage 2-7.)
The tbinit daemon also schedules the work of the page-cleaner daemons. If
no page-cleaner daemons exist, tbinit takes over page-cleaning responsibil-
ities. (Refer topage 2-74 for a detailed explanation of buffer page flushing,
which is the responsibility of the page-cleaner daemons.)