Distributed Systems Network Management (DSNM) Subsystem Interface Development Guide

I Process Program Structure Concepts
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109759—Distributed Systems Network Management (DSNM) Subsystem Interface
Development Guide
I Process Development Process
Dispatch
Dispatch means invoking a thread for execution.
A thread procedure periodically suspends execution until something occurs (for
example, the completion of an I/O operation) by returning to the frame with a RETURN
procedure and waiting for the frame to generate a particular event, at which point the
frame dispatches the current thread procedure. (See the “Event” discussion next in this
subsection.) As the thread executes, it can alter the current thread procedure to be called
by the frame at the next thread dispatch.
When execution proceeds after an event, the current thread procedure is reentered from
the beginning. The thread procedure determines its current state from the event that
occurred and information stored in its context area (see the “Command Context”
discussion later in this subsection).
Library routines help support state maintenance and restoration. Local variables are not
preserved and must be reinitialized on continuation after any return to the frame.
Event
An event is an occurrence that initiates a thread dispatch. Whenever a thread is
dispatched, the event that caused the dispatch is communicated to the thread.
Figure 3-2. Relationship Between the Frame and User-Written Procedures
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I Process Program Frame
Command Thread
Procedure
Subprocedures
Command Thread
Procedure
Subprocedures
_COMMAND^PROC
_STARTUP^MODE_STARTUP
Command Thread
Procedures
Subprocedures
User-Written
Procedures
I PROCESS
_COMMAND^
TERMINATION^
PROC