OSI/AS Management Programming Manual

1 Introduction
056785 Tandem Computers Incorporated 1–1
The Tandem OSI/AS (Open Systems Interconnection/Application Services) subsystem
provides a Session Layer, Presentation Layer, and Association Control Service Element
(ACSE) interface to OSI networks. OSI/AS requires Tandem OSI/TS, plus one of the
following Tandem access methods:
X.25 Access Method, X25AM (for wide area networks)
Tandem LAN Access Method, TLAM (for local area networks)
OSI/AS supports the Distributed Systems Management (DSM) facilities provided by
Tandem for subsystem management. DSM provides two types of management
interfaces to subsystems: commands that perform operations on subsystem objects,
and event messages that report significant events detected by the subsystem.
Commands provide a two-way interface: a human operator or management
application sends a command to a subsystem, and the subsystem then performs some
action and returns a response to the operator or application. Event messages, on the
other hand, provide a one-way interface: information flows from the subsystem to the
operator or management application, but no information flows in the other direction.
Note When the terms event and token appear in this manual, they refer to DSM events and tokens, as defined
in the Distributed Systems Management (DSM) Programming Manual and the other DSM manuals.
Except where explicitly stated, they do not refer to OSI Session Layer, Presentation Layer, or ACSE
events or tokens.
For commands and for event messages, OSI/AS supports both interactive and
programmatic interfaces.
The Subsystem Control Facility (SCF) is an interactive interface that allows a human
operator to send DSM commands to Tandem data communications subsystems,
including OSI/AS. The Event Management Service (EMS) includes printing and
compatibility distributor processes that can print or display event messages for
operators, and the ViewPoint console application includes screens that allow selective
viewing of event messages.
The DSM programmatic interfaces for sending commands (control and inquiry) and
retrieving event messages (event management) allow programs to perform the same
kind of monitoring and control operations that users of SCF, EMS printing and
compatibility distributors, and ViewPoint can perform interactively. This manual
describes the DSM programmatic interfaces to the OSI/AS subsystem.
Why Management
Programming for
OSI/AS?
In some situations, it is desirable to use a programmatic interface, rather than an
interactive interface, to manage a subsystem such as OSI/AS. This is true for the
following reasons:
It is efficient to transfer as many routine network-management tasks as possible to
programs running on the computer network, freeing operators and other network-
management personnel to do the work that requires judgment and creativity.