SPI Common Extensions Manual

Introduction to SPI Extensions
SPI Common Extensions Manual—427508-001
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Management Applications
The definition of a logical object depends on the subsystem that uses it. For example,
in an X25AM subsystem, a subdevice, which is a logical object, represents a circuit,
the real object.
Management Applications
Management applications use SPI to help them configure, control, monitor, and report
the status of subsystem objects. The primary tasks of a management application differ
from those of other applications. Rather than using a subsystem’s basic services, a
management application monitors and controls the subsystem itself.
Because management tasks can be complex, repetitive, or time consuming, they lend
themselves to programmatic solutions. Hence the value of management applications,
which you can design to manage individual subsystem objects or entire subsystems.
Management applications perform such tasks as:
•
Starting or stopping an object (such as a Pathway terminal)
•
Changing the value of an object attribute (such as the speed of a communications
line)
•
Adding a new object to the system (such as defining a logical subdevice on a
communications line)
•
Inquiring about whether an object is running
Subsystem Managers
Every subsystem that has an SPI command/inquiry interface includes a process
responsible for supporting the interface. This process—the subsystem manager
process or subsystem manager—uses SPI to communicate with management
applications and is the process to which management applications send SPI
commands.
SPI Message Protocol
Communication between a management application and a subsystem follows the
standard Compaq requester-server model, with the management application in the role
of requester and the subsystem manager process in the role of server.
Instead of communicating directly with management applications, a subsystem can
have its commands and responses routed through an intermediate process. Extended
SPI provides such a process—the Subsystem Control Point (SCP).
SPI is a general interface governed by many general rules and guidelines. For the
basic SPI protocol, SPI procedures used to build messages, and common data
definitions used in SPI messages, see the SPI Programming Manual .
This manual describes common extensions to the basic SPI interface. The SPI
interface to a particular subsystem is usually based on an even more specific