SNAX/APC Application Programming Manual

Using the Application Program Interface
SNAX/APC Application Programming Manual—138786
1-6
SCREEN COBOL Transaction Programs
You do not have to activate and deactivate LU sessions just because SNAX/APC makes
the verbs available. It may be the responsibility of your network support staff to control
sessions. Just as adding and starting LUs is not really the responsibility of the
application programmer, so starting and ending sessions need not be your responsibility
either.
Complete operator control is provided interactively by SCF and programmatically by the
management programming interface to SNAX/APC.
See the SCF Reference Manual for SNAX/APC and the SNAX/APC Management
Programming Manual for further details.
SCREEN COBOL Transaction Programs
SNAX/APC TPs can be written as SCREEN COBOL program units executed by TCPs.
SCREEN COBOL TPs can communicate with a SNAX/APC process in one of two
ways:
•
Define SNAX/APC as a Pathway server. In this case, the SCREEN COBOL TP
uses the SCREEN COBOL Send statement to communicate with SNAX/APC.
•
Use Pathway (Pathway/TS) Intelligent Device Support (IDS) and define SNAX/APC
as an intelligent device. In this case, the SCREEN COBOL TP uses the SCREEN
COBOL SEND MESSAGE statement to communicate with SNAX/APC.
In both cases, the SCREEN COBOL TP must issue requests exactly the same as a TP
written in any other programming language. Each request must begin with an IPC
header followed by one or more UOWs. The reply contains the reply IPC header,
followed by the reply UOWs.
A SCREEN COBOL TP differs from other TPs mainly because SCREEN COBOL TPs
cannot be started by the SNAX/APC Dispatcher. SCREEN COBOL TPs must be run or
started as terminal threads. SCREEN COBOL TPs do not receive DISPATCH-TP
UOWs. They must begin processing by sending a TP-READY request to the
SNAX/APC server. (For more information on starting SCREEN COBOL programs, see
the NonStop TS/MP and Pathway System Management Guide.)
Data Areas
Data areas for the (MC)RECEIVE-AND-WAIT, (MC)RECEIVE-IMMEDIATE, and
(MC)SEND-DATA verbs must include space for the actual data (RWR-DATA-AREA,
RIR-DATA-AREA, and SD-DATA-AREA). Unfortunately, definitions for these areas
are application-dependent (which DDL will not support), and mechanisms for reserving
space are highly language-dependent.
Instead of defining these areas using DDL, you must add the language-specific data-area
definitions for the following within your own application:
RWR-DATA-LENGTH
RWR-DATA-AREA
RIR-DATA-LENGTH
RIR-DATA-AREA
SD-DATA-LENGTH
SD-DATA-AREA