Introduction to TRANSFER Delivery System

The TRANSFER Delivery System TRANSFER Applications
Introduction to TRANSFER Delivery System—109426 1-7
TRANSFER Applications
A TRANSFER application is a group of processes or PATHWAY online transaction
processing systems that use TRANSFER to communicate with each other. Tandem
provides several electronic mail applications: PS MAIL for Tandem 6530 terminals (or
terminal emulators), PS MAIL for IBM 3270 terminals, and PS MAIL for TTY
terminals. You can write extensions to your PS MAIL application to satisfy your
particular package delivery requirements.
In a typical TRANSFER application, such as a PS MAIL one, you start a transaction by
composing a memo at a terminal. Along with the text, you specify recipients for the
memo, a timeframe during which the memo is to be delivered, and how long the memo
should be held for its recipients. Then you press a function key in PS MAIL 6530 and
PS MAIL 3270, or type the SEND command in PS MAIL TTY, to send the memo. The
application makes requests to TRANSFER to build the package that contains the memo
and to send it. TRANSFER sees that the package is delivered to each recipient.
Application programmers who want to base their applications on TRANSFER usually,
though not necessarily, write in SCREEN COBOL. SCREEN COBOL is a language
that specifies screen formats and instructions for controlling terminals.
Such user-written applications typically perform the following functions:
■ Communicate with people at terminals
In each PATHWAY system, SCREEN COBOL program units running in terminal
control processes (TCPs) provide the interface to the operator using the application.
TCPs are programs supplied by Tandem to interpret SCREEN COBOL object code.
If communicating PATHWAY systems support different business functions—for
example, if one system supports finance and another supports purchasing—the
correspondents do not necessarily use the same operator interface.
■ Build and send packages for delivery
SCREEN COBOL program units specify what goes into a package, who should get
the package, and what constraints—such as expiration dates and times—apply to the
delivery. The building and sending of a package involves several SCREEN
COBOL SEND statements to TRANSFER server processes, which perform the
application request and send back replies. Servers are the parts of an application
that deal with the database itself, handling everything related to the application
computations and database access.
■ Retrieve and respond to packages
SCREEN COBOL program units retrieve incoming packages—and can store them
for later use—by issuing SCREEN COBOL SEND statements to TRANSFER
servers.