IBM System/370 145 Manual page 65

their own individual value, they 1too, either indirectly or directly,
ease the installation of newapp1jications.
potential for Increased New I\Ppli4::ation Development
The following capabilities are characteristic of a virtual storage
operating system environment:
• Greater f1exibility in the de;ign of applications is possible.
Larger programs can be written without the necessity of using
planned overlay techniques or other dynamic
pr~am
structures
designed to fit programs.iato the amount of real storage available.
The need for intermediate (or working) data sets is reduced or
eliminated because tables, reJLatively small data groups, etc., that
are placed on direct access s1:orage because of real storage
limitations, can beCOJDe part of the program and will be brought into
reaJL storage automatically as required. Program planning, coding,
and testing time can be reduCEn by elim1nation of the use of these
programming techniques and other real storage management facilities,
which aJLso require additional programming skill and knowledge. Also
avoided is the restructuriing of application programs after they have
been written, because they
arE!
larger than the real storage
available for their execution., Bence, applications can become
operational more quickly.
Open-ended, straightforward aI~1ication design is possible and more
comprehensive programs
can
be written.
An application can be
segmented into a series
o~ prc~ams
according to its logical flow
instead of according to the
~lnctions
that can be performed in the
specific amount of real
stora~re
avai1able to each step in the
application. programming: and processing duplication inherent in the
approach of using two or
~re
job steps to perform one logical
process is thereby avoided.
Additional programming facilit:ies can become available that
otherwise could not
be
used bE~ause of real storage limitations.
Specifically, full function bj~h-level language translators, which
offer more capabilities than their subset versions (such as
additional debugging facilitiES and performance options) but which
also have larger storage desi~~ poin1ts, can be used because they can
operate in a virtual storage EDvironment using less real storage
than their design point requ:iJ:·ement.
• Preproduction· testing of
large~
than average application programs
can be increased if enough viztua1 storage Can be made available to
enable them to run during nOCllal testing periods. Turnaround time
during testing can be reduced.
In a nonvirtual storage Environment such programs are usually
grouped together and exe~ted only at certain times when their
larger design point storage requirements can be made available.
• Fine tuning of application pro~ams
to
achieve performance
improvements, when necessary. can
be
delayed until after the
application is in production. TbJis capability enables an
application to become operative sooner.
• startup costs for new applications may
be
reduced.
A new application can be developed and tested on the existing
system, assuming the required I/O devices are present in the
configuration, before the additional real storage the application
requires for performance on a production basis is actually
installed. When the application is ready for production, the
A Guide to the IBM System/370 Mode.l
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