Introduction to Data Management

Managing Data on the Tandem Systems
2-8 15873 Tandem Computers Incorporated
Figure 2-3. Adding New Applications
Inventory
Control
Application
S8020-006
Tandem System
Materials
Requirement
Planning
Application
Bill-of-
Materials
Application
You can also easily modify selected portions of an existing process to suit your
changing needs, leaving the rest of this process—and other processes—intact.
Suppose, for instance, that you are working on an order-processing application where
one process adds a customer’s name to the database, a second process runs a credit
check, a third adds an order to the database, and a fourth deletes the ordered items
from inventory. If your credit-checking criteria should change, you can alter the
credit-checking module without affecting any of the other modules.
Most of the products that help you build and maintain expandable applications are
part of the Tandem data management software described throughout this manual. By
automatically furnishing continuous operation for NonStop transaction processing,
these Tandem products eliminate the need to code process-pair support explicitly in
your application software.
A primary feature of the data management software is its provision for relational
databases, which offer you enormous flexibility. In a relational database, no rigid
predefined relationships, which are difficult to alter, need to exist among files. The
interfile relationships are determined only by values in key fields that are common to
those files.
The data management software lets you access records using any of 255 possible
alternate-key fields. Because you need not predefine these fields, you can combine
and recombine information in an existing database in many innovative ways. As your
application requirements change, you can easily incorporate your changes without
redesigning the database, moving files about, or recoding your programs.
Another kind of flexibility comes from the file system, which functions as part of the
GUARDIAN 90 operating system. The file system allows application processes to
access all devices in a uniform way, treating all terminals, disks, portions of disks, and
even processes, as files. File names are assigned to devices when the system is
configured, to disk files when they are created, and to processes when they are run.