
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 a D (daemon) flag or
an F (page cleaner or “flusher”) flag in the fourth flag position of the user
entry.
tbinit Daemon
Thetbinit daemonisspawnedbythetbinit processearlyintheinitialization
process. The tbinit daemon occupies the first entry in the shared-memory
user table, which is represented by the first entry in tbstat -u output.
The tbinit daemon is responsible for most of the tasks of disk space and
shared-memory initialization. (Refer to page 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 to page 2-74 for a detailed explanation of buffer page flushing,
which is the responsibility of the page-cleaner daemons.)
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