IBM 1130 User Manual page 435

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CONVERSION METHODS
There are three common methods for conversion:
1. Parallel operation. With this method, the same
transactions are entered into both the old and the
new systems, and the controls are compared. This
process is continued over a predetermined (usually
short) period of time, until a responsible executive
is satisfied that the new results are accurate.
Make sure that the time period of parallel
operation is one during which a wide variety of
transactions occur. Large volume is not important,
but variety is, since you want to test as many as-
pects of the new systems as possible. Pick a slow
time in your business cycle to effect conversion.
Before starting parallel operations, obtain a'
clear understanding of what is to be checked, and by
whom. Since additional personnel or man-hours
will be needed during this period, avoid conflicts
with vacation and holiday schedules.
As far ahead of the parallel period as possi-
ble, the personnel who will be preparing the input
cards for the new system should gain experience in
using the new input document and card formats.
This is one of the most common areas of difficulty,
and many "computer" mistakes are eventually traced
back to faulty document preparation, accumulation
of controls, or card punching. Often it is possible
to use new formats exclusively some time before
the computer system arrives, by preparing cards in
the computer-required formats and then reproducing
them into the old formats for use by the current
system.
Parallel operations often encounter problems
that result from significant differences between the
procedures used in the old system and those in the new.
It
may be quite difficult to compare results produced
by the two systems, since the important totals in the
new system may not have been prepared previously.
Or you may find it possible to print reports in a
desirable sequence which is not feasible currently,
but which will make it impractical to cross-check
line-items against reports in the old sequence.
Another problem inherent in parallel opera-
tions is the doubled probability of errors. There
are twice as many chances for errors to occur, and
when making up a schedule, you must consider the
time spent in tracking errors down and deciding
which system, if either, was right.
2. Pilot Operation. In pilot as in parallel opera-
tion, an application is run under both the old and the
new systems. The difference lies in selecting only
one or a few easily observed locations or depart-
ments within the company, and performing the
operation only for those sections rather than for the
entire company. The same care must be taken in
setting up controls, scheduling the period during
which the pilot operation is to take place, and train-
ing those who prepare the input. In regard to this
last problem, the pilot method offers a training
ground for those who prepare and punch the data, by
allowing different people to get experience every day
or every few hours.
Care should be taken in determining which
part of the job is selected for pilot running. It
should be completely independent and self-contained,
if possible. Therefore, pilot operations may be the
ideal choice for organizations that are divided into
fairly independent units or locations. In any case,
the effect of the pilot run on departments other than
the data processing department must be carefully
analyzed, and those who are affected should be noti-
fied we 11 ahead of time.
Again, you must carefully establish who is to
do what and when, if an adequate analysis of the pro-
gress and success of the operation is to be made.
3. One-time cutover. As of a given date, the
old system is discontinued and the new system is put
into operation. Careful planning is necessary to
make the transition smooth. For one thing, files
can be built up during a fairly extensive period be-
forehand and checked with control figures for accu-
racy and completeness while being created .. A
master file of customers can be card-punched
during the month before the preparation of state-
ments. Alternatively, only new customers' cards
can be punched, while operations are performed on
the old file to convert them into the new format.
Then both the old and new cards are merged at
month end to create an updated master file ready for
use by the new system.
It
is often desirable to write
one-time programs to do these file conversions.
Whether the computer or other equipment is used,
time must be scheduled for the coding or procedure
writing, as well as for the operation itself.
Where some data is to be recoded, or coded
for the first time, as in the assignment of a new or
better set of customer numbers, you should get the
job done and checked out in advance.
Another way of smoothing the cutover is to
maintain control procedures that will be required
for both the old and new systems some time before
the critical date. This will eliminate the possibility
of errors in the execution of these procedures.