GDSX Management Programming Manual

GDSX Management Programming Manual—529930-001
2-1
2 Communicating With GDSX
This section provides subsystem-specific information about the tokens used to
communicate with the GDS subsystem. General information about tokens can be
found in the SPI Programming Manual, and information about tokens that is common
to all data communications subsystems can be found in the SPI Common Extensions
Manual.
Understanding Tokens
The commands, responses, and event messages that are sent to and received from
the GDS subsystem are made up of special codes called tokens. Each token contains
a particular piece of information, such as the command number of a command or one
element of an event message. Tokens can be single values or structures consisting of
several values, and some tokens, called header tokens, are present in every
command, response, or event message
To understand tokens, you should be familiar with the data definition language (DDL).
See the SPI Programming Manual for an explanation of DDL.
The Subsystem Programmatic Interface (SPI) is used for building commands to,
decoding responses from, and obtaining event messages issued by the GDS
subsystem. The procedures used by an application to perform these tasks are
described in the SPI Programming Manual.
Definition Files
Every token or other type of definition needed by an application that uses SPI is
defined in definition files provided by HP. Each source of definitions, such as a
subsystem or an operating-system component, has associated with it a set of four
definition files: one in TAL; one in COBOL85; one in TACL; and one in DDL, from
which the other three definition files are derived.
To be able to use the definitions from a particular source, an application copies or
loads the definition file associated with that source that is in the appropriate
programming language. The definitions in a COBOL85 definition file are grouped into
sections to enable COBOL85 programmers to declare multiple copies of structures in
the definition file. TAL programmers should always source in the entire definition file,
and TACL users should load the entire definition file. For further information on how
definition files are accessed by an application, refer to the SPI Programming Manual.
An application that communicates with the GDS subsystem needs the following
definition files in the appropriate programming language:
•
SPI definition file
•
EMS definition file (needed only if the application retrieves event messages or
controls EMS)