Introduction to TRANSFER Delivery System

PATHWAY—Online Transaction Processing The TRANSFER Delivery System
1-14 109426—Introduction to TRANSFER Delivery System
PATHWAY solves several problems for the programmer:
■ PATHWAY provides a model for dividing the work of an application. Requesters
control terminals, validate data, and present information to users. Servers accept
requests for transactions, manipulate the database, and reply.
■ PATHWAY lets one terminal control process (TCP) control multiple requesters;
each requester maintains the data that one terminal requires. The TCP moves
among multiple sets of SCREEN COBOL program units.
■ PATHWAY provides online load balancing, with or without operator intervention,
by dynamically creating copies of servers when the workload increases and by
deleting copies of servers when the workload slackens. Identical servers running in
the same PATHWAY application constitute a server class. A SCREEN COBOL
program that calls upon a server can communicate with any member of the specified
server class.
Figure 1-7 illustrates a PATHWAY application with multiple terminals, TCPs, server
classes, and a distributed database.
Figure 1-6. Requesters and Servers in PATHWAY
Application
and Database
Logic
Read
Reply
S8123-006
Display to
Screen
Accept Input
Send to
Server
Receive Reply
From Server
Requester
Server
Class A
Server
Class B
Server
Class C
Requester Server
NonStop
SQL
ENSCRIBE
Application
Requester
Requester