OSI/MHS Orientation Guide

Glossary
OSI/MHS Orientation Guide—424829-001
Glossary-28
Port Access Method (PAM)
transport layer. Layer 4 in the OSI Reference Model. This layer provides reliable,
transparent transfer of data between end systems and ensures that the data arrives at the
correct destination.
transport selector. See TSEL.
TSAP (transport service access point). A logical location between the Transport and Session
Layers, through which transport services are made available to local users, and through
which session services are made available to remote systems.
TSEL (transport selector). An address between the Transport and Session Layers, through
which connections are established and maintained. A single TSEL can service one or
more connections simultaneously and can refer to one or more TSAPs.
TSP process. The OSI transport services process.
type. See attribute type.
UA (user agent). The functional component that represents the user in an X.400 message
handling system. A UA interacts directly with the user, prepares messages, and submits
messages for routing to their destinations. UAs also reply, retrieve, and potentially
forward messages for the user. See also RUA and LUA.
unconditional token. A token that is always present in a particular event message. See also
conditional token.
unreserved object. In the GPI, an object on the input queue that is not reserved by a client
program. A client program must reserve the object to examine or copy it.
user agent. See UA.
user database. A database in the OSI/MHS database that contains records of APPL objects.
Each APPL object corresponds to a user agent or a gateway.
user message. An octet string, which can be of a standardized content type, such as IPM or
EDI. A user message can contain one of a variety of encoded information types, such as
text, facsimile, graphics, or voice.
value. See attribute value.
value position. The position of a value of a multivalued attribute.
Viewer. See NSDS Viewer.
ViewPoint console application. An extensible interactive application for operators, provided
as part of DSM. ViewPoint allows a system or a network to be controlled from a single
terminal. It includes several block-mode display screens for event messages, a block-
mode display for system or network status, a conversational TACL screen, and a facility
called Define Process to maintain sessions with multiple subsystems at the same time.
wait manager process. A type of queue manager process.
warning. In DSM interfaces, a condition, encountered in performing a command or other
operation, that can be significant but does not cause the command or operation to fail. A
warning is less serious than an error.