IBM System/370 145 Manual page 56

program development time is spent designing the inquiry program
to operate with a dynamic overlay structure so that only 12K of
processor storage is required for its execution.
4. A multiprogramming installation has a daily workload consisting
primarily of long-running jobs. There are also certain jobs that
require a relatively smal~ amount of time to execute. The times
at which these jobs must
be
executed is unpredictable; however,
when they are to be run, they have a high completion priority.
While it is desirable to
be
able to initiate these high-priority
jobs as soon as the request to execute them is received, this
cannot be done because long-running jobs are usually in
operation. Hence, a certain time of day is established for
initiating high-priority jobs, and the turnaround time for these
jobs is considerably longer than is desired.
5. A series of new applications are to be installed that require
additional computing speed and twice the amount of processor
storage available in the existing system. The new application
programs have been designed and are being tested on the currently
installed system until the new one is delivered. However,
because many of the new application programs have storage design
points that are much larger than those of existing applications,
testing has to be limited to those times when the required amount
of processor storage can
be
made available. Although another
smaller scale model is also installed that has time available for
program testing, it cannot be used because it does not have the
amount of processor storage required
by
the new application
programs. In addition, although the smaller scale model now
provides backup for the currently installed larger scale model,
the smaller scale model cannot be used to back up the new system
because of processor storage size limitations.
6. A large terminal-oriented application is to be operative during
one entire shift. During'times of peak activity, four times more
processor storage is required than during low activity periods.
Peak activity is experienced about 20 percent of the time and low
activity about 40 percent. The rest of the time, activity ranges
from low to peak. Allocation of the peak activity processor
storage requirement for the entire shift cannot be justified and
a significantly smaller storage design point is chosen. As a
result, a dynamic program structure must be used, certain desired
functions are not included in the program, and response times
during peak and near-peak activity periods are increased above
that originally planned.
In this installation, most of the batched jobs are processed
during the second shift. However, there is also a need to
operate the large terminal-oriented application for a few hours
during second shift. This cannot be done because the system does
not have the amount of processor storage required for concurrent
operation of the batched jobs and the terminal program (which
must have its storage design point amount allocated even though
that amount of processor storage would not
be
required during
second shift operations). The large amount of additional
processor storage required to operate the terminal program for
only a portion of the second shift cannot be justified.
7.
An
application program with a very large storage design pOint is
executed only once a day as a hatched job. A significant benefit
would result from putting the program online to a few terminals
during the morning hours. However, the program continues to be
run as a hatched job, because it is very large and would be made
larger by putting it online. The large amount of additional
46 A Guide to the IBM System/310 Model 145