OSI/MHS Gateway Programmatic Interface (GPI) Reference Manual

Glossary
OSI/MHS Gateway Programmatic Interface (GPI) Reference Manual—522223-001
Glossary-26
segment
instance of this process, which in turn sends the commands on to the manager processes
of the target subsystems. SCP also processes a few commands itself. It provides
security features, version compatibility, support for tracing, and support for applications
implemented as NonStop™ process pairs.
segment. See string segment.
selector. In OSI, an address component that refers to one or more service access points
(SAPs) of the Transport, Session, or Presentation Layer and is used to establish and
maintain connections. Remote systems and local users specify the selectors as part of an
address called the “n-address.” See also SAP.
send file. In the P7 API, a file used for sending data to the OSI/MHS subsystem. The file
number is returned by a call to the LOS_OPEN_ procedure. See also result file.
sensitive command. In DSM, a command that can be issued only by a restricted set of
Guardian 90 users, such as the owner of a subsystem process. For Compaq data
communications subsystems, the sensitive commands are those that can change the state
or configuration of objects, start or stop tracing, or change the values of statistics
counters. See also nonsensitive command.
service. A set of primitives (operations) that an OSI layer provides to the layer above it. The
service defines what operations the layer can perform on behalf of its users, but not how
these operations are implemented. A service relates to an interface between two layers,
with the lower layer being the service provider and the upper layer being the service
user. See also protocol.
The GPI and P7 API are examples of services available to applications. In both cases,
the service consists of a process and the library procedures that provide the application
interface to that process.
service access point. See SAP.
service element. In OSI, a feature or function defined as part of a service.
service primitive. In OSI, an abstract, implementation-independent interaction between a
service user and a service provider. Service primitives describe the sequences of events
between adjacent layers that occur through the service access point (SAP). There are
four types of service primitives; see confirm primitive, indication primitive, request
primitive, or response primitive.
session. A temporary logical connection between a user and a software product, or between
communicating processes.
In the GPI, an interaction between a client program and the GPI, established when a
client program successfully calls the GPI_OPEN_ procedure. Once a session is
established, the client program can request GPI services by calling other GPI
procedures. A session is ended by calling the GPI_CLOSE_ procedure.
In the P7 API, an interaction between a client program and an LO group, established
when a client program successfully calls the LOS_OPEN_ procedure. Once a session is