TS/MP Pathsend and Server Programming Manual (G06.24+, H06.03+)

Introduction to Pathway Application Programming
NonStop TS/MP Pathsend and Server Programming Manual–132500
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The Pathsend Environment
SCREEN COBOL Requesters
SCREEN COBOL requesters, which are compiled by the SCREEN COBOL compiler
and then interpreted and executed by the terminal control process (TCP), provide ease of
programming if you need to handle large numbers of terminals or intelligent devices or
if you need screen-presentation services. The TCP and the SCREEN COBOL language
produce a high-quality, manageable application. The TCP provides multithreading of
requesters, fault tolerance, terminal device configuration, and operations management so
that you do not need to program these features in your application. Transaction
protection through use of the TMF subsystem, with simplified programming, and
automatic retry of I/O operations are also provided. SCREEN COBOL requesters are
described in the Pathway/TS TCP and Terminal Programming Guide and the
Pathway/TS SCREEN COBOL Reference Manual.
You can use an Extended General Device Support (GDSX) process as a front-end
process to the TCP and SCREEN COBOL requesters to communicate with devices not
directly supported by the TCP. Use of the GDSX product is described in the Extended
General Device Support (GDSX) Manual.
The Pathsend Environment
The Pathsend environment includes Pathsend processes and LINKMON processes:
•
Pathsend processes, written as part of your application, use Pathsend procedure calls
to make requests to server classes.
•
LINKMON processes, supplied by Tandem, control communication between
Pathsend processes and Pathway server classes.
Pathsend Processes
In writing programs to run as Pathsend processes, you use a set of procedures that are
part of the Guardian procedure library. These procedures allow you to send request
messages to server processes within a server class and to receive the servers’ replies.
You can call the Pathsend procedures from programs written in C, C++, COBOL85,
Pascal, the Transaction Application Language (TAL), or the Portable Transaction
Application Language (pTAL).
Pathsend procedure calls are provided for both context-free and context-sensitive
communication with servers. A context-free server accepts a single message from a
requester, performs the requested tasks, and issues a single reply to respond to the
requester. After the reply message is issued, the server retains no information (context)
that can be used in subsequent requests. A context-sensitive server engages in a
multiple-message communication, or dialog, with a requester. Between messages, the
server retains information (context) pertaining to the dialog.
The use of the Pathsend procedure calls is described in Section 3, Writing Pathsend
Requesters, and their syntax is described in Section 5, Pathsend Procedure Call
Reference. Design considerations related to context-free and context-sensitive servers
are discussed in Section 2, Designing Your Application.