Systems Analysis & Design:
- Conversion involves transferring all necessary data from the
old to the new system and bringing the new system into operation.
- The analyst is actively involved in planning the conversion
so that it will cause the least possible disruption to the daily
operations of the business.
There are many conversion strategies available to analysts, and
there is also a contingency approach that takes into account several
organizational variables in deciding which conversion strategy
- These is no single best way to proceed with conversion.
- The importance of adequate planning and scheduling of conversion
(which often takes many weeks), file backup, and adequate security
cannot be overemphasized.
- Conversion strategies include direct changeover, parallel
conversion, gradual conversion, and phased conversion.
- Conversion by direct changeover means that, on a specified
date, the old system is dropped and the new system is put into
- Direct changeover can only be successful if extensive testing
is done beforehand and it works best when some delays in processing
can be tolerated.
- Direct changeover is considered a risky approach to conversion,
and its disadvantages are numerous.
- For instance, long delays might ensue if errors occur, since
there is no alternate way to accomplish processing.
- Additionally, users may resent being forced into using an
unfamiliar system without recourse.
- Finally, there is no adequate way to compare new results with
- This refers to running the old system and the new system at
the same time, in parallel.
- This is the most frequently used conversion approach.
- Both systems are run simultaneously for a specified period
of time, and the reliability of results is examined.
- When the same results can be gained over time, the new system
is put into use, and the old one is stopped.
- The advantages of running both systems in parallel include
the possibility of checking new data against old data in order
to catch any errors in processing in the new system.
- Parallel processing also offers a feeling of security to users,
who are not forced to make an abrupt change to the new system.
- There are many disadvantages to parallel conversion including
the cost of running two systems at the same time and the burden
on employees of virtually doubling their workload during conversion.
- Another disadvantage is that unless the system being replaced
is a manual one, it is difficult to make comparisons between outputs
of the new system and the old one. If the new system was created
to improve on the old one, then outputs from the systems should
- Finally, it is understandable that employees who are faced
with a choice between two systems will continue using the old
one because of their familiarity with it.
- Gradual conversion attempts to combine the best features of
the earlier two plans, without incurring all of the risks.
- The volume of transactions handled by the new system is gradually
increased as the system is phased in.
- The advantages of this approach include allowing users to
get involved with the system gradually and the possibility of
detecting and recovering from errors without a lot of down time.
- Disadvantages of gradual conversion include taking too long
to get the new system in place and its inappropriateness for conversion
of small, uncomplicated systems.
- This refers to a situation in which many installations of
the same system are contemplated.
- One entire conversion is done (with any of the approaches
considered already) at one site.
- When that conversion is successfully completed, other conversions
are done for other sites.
- An advantage of phased conversion is that problems can be
detected and contained, rather than inflicted simultaneously on
- A disadvantage is that even when one conversion is successful,
each site will have its own peculiarities to work through, and
these must be handled accordingly.
- The analyst must consider many factors (including the wishes
of clients) in choosing a conversion strategy.
- No particular conversion approach is equally suitable for
every system implementation.
- Regardless of the conversion method, a changeover date, usually
at the end of a business period, must be chosen so as to minimize
disruption to the organization.
- There must be some type of a plan to fall back on in case
major defects appear in the new system.
- The fallback plan must make provision for not only the system
to be used, but also the personnel and supplies that the system
- With parallel operation, use of the old system can be resumed.
- With direct conversion, however, the old system may not be
up to date, and therefore going back to it may be difficult.