Introduction to TRANSFER Delivery System

Introduction to TRANSFER Delivery System—109426 1-1
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The TRANSFER Delivery System
Overview
The TRANSFER delivery system is a high-level software product that supports
communications between people, input-output (I/O) devices, and running programs
referred to as processes. TRANSFER provides a set of processes that build, maintain,
and route packages of data to requesting applications.
A TRANSFER package is a collection of information. A package of interoffice mail
might include text and pictures sent and received by people working at the same or
different locations. A package of data needed to update a database might include
numbers and transaction codes sent by one process, such as one for entering orders, to
another process, such as one for manufacturing.
Senders and receivers of packages can be located anywhere in a Tandem EXPAND
network and can be associated with different applications. Figure 1-1 shows various
applications that can be developed to use TRANSFER as the delivery system, sending
packages to a person at a terminal, to a printer, and to a process in another application.
TRANSFER offers a delivery system that is:
■ Flexible
A user can say what goes into a package of data: what kinds of data, how much, and
in what arrangement. A user can communicate with any other user anywhere in the
network and can specify delivery parameters; for example, “Deliver this package
tomorrow,” or “Certify delivery to each recipient.”
■ Reliable
The package reaches its destination even if a recipient or network node is
temporarily unavailable, if a communication line or disk controller fails, or if a
system has to be reloaded. When a package cannot be delivered right away, it is
delivered later; the sender does not have to resend the package. A recipient need not
be present for a package to arrive; recipients retrieve packages at their own
convenience.
■ Easy to use
TRANSFER does not make great demands on programmers or on operators. The
programming interface is straightforward and allows designers to make efficient use
of computing resources. For example, a transaction to send a package to 17 people
requires one statement, not 17, and the application is able to proceed while the
package is being routed. A user can send another package or start another
transaction before the first package is successfully delivered.