SNAX/APC Management Programming Manual

Glossary
Glossary–4 111813 Tandem Computers Incorporated
Expand network. A network consisting of Tandem systems interconnected by
communication links and supported by Expand software.
finite state machine. An algorithm that controls the transition of an object — for
example, a SNA session — between a finite number of states, each state transition
being generated by one of a finite number of events.
first speaker. In SNA, the LU-LU half-session defined at session activation as: (1) able to
request a bracket without requesting permission from the other LU-LU half-session to
do so, and (2) winning contention if both half-sessions attempt to begin a bracket
simultaneously. Contrast with bidder.
FM. Function management.
FMD. See function management data.
function management data (FMD). In SNA, an RU category used for end-user data
exchanged between logical units and for requests and responses exchanged between
network services components of LUs, PUs, and SSCPs.
function management (FM) header. In SNA, one or more headers optionally present in the
leading request units of an RU chain that allow a half-session in an LU-LU session to
transmit control information for the data that follows.
GDS. See general data stream.
GDS variable. A general data stream block that begins two-byte length followed by a
two-byte ID field.
general data stream (GDS) A data stream syntax in which data is formatted as a series of
blocks called GDS variables, each of which begins with a two-byte ID length followed
by a two-byte ID field.
half-session (HS). In SNA, a component that provides function management data
services, data flow control, and transmission control for one of the sessions of a
network addressable unit.
host. A general–purpose processor, such as an IBM 3033, that contains an SSCP, PU
type 5 logic, and one or more LUs representing different applications or application
subsystems.
HS. See half-session.
independent verbs. Verbs that can be used in either basic or mapped conversations.
SNAX/APC supports only GET-TYPE.
I/O process. A system process to manage I/O hardware. Applications use the
operating file system to send requests to I/O processes.
IPC. See interprocess communication.
IPC version code. A code used by SNAX/APC to identify the version of the verbs
available to a transaction program; for example, S1, S2, and S3. The code is carried in
the IPC message header.