Week 9

In Shelly, Cashman and Rosenblatt (2006), system changeover is defined as the process of putting the new information system online and retiring the old system. Four approaches to changeover have been identified in the textbook, direct cutover, parallel operation, pilot operation and the last approach is phased operation. Changeover can be rapid or slow, depending on the method selected or implemented.

Direct cutover as the name suggests is an instant changeover from the old system to the new. Parallel operation is a slowest method as it requires both, the new and the old system to run simultaneously for a specific period. On the other hand, pilot operation and phased operation fall between direct cutover and parallel operation. Each of these approaches has their own benefits and problems associated with their implementation.

Direct Cutover:
As mentioned above, direct cutover approach causes the changeover from old system to the new system to occur instantly. This approach is least expensive for changeover as the IT group has to operate and maintain only one system at a time. The down side of this approach is that direct cutover involves more risk then other approaches. Some problems can occur during direct cutover when the system goes into operation. Problems can result from data situations that were not tested or from errors caused by users. Another disadvantage of implementing direct cutover is that detecting minor errors becomes difficult as users cannot verify current output by comparing it to output from the old system. Many companies choose the direct cutover approach for implementing commercial software packages because they feel that commercial packages involve less risk of total system failure.

Timing is an important element to be considered while choosing the direct cutover approach. This is because most systems can operate on weekly, monthly, quarterly and yearly cycles. For systems developed in house, most companies use direct cutover for non critical situations. It may also be the only choice, if the operating environment cannot support both the old and new systems or if the old and new systems are incompatible.

Parallel Operation:
This kind of changeover involves both the old and the new information systems to operate fully for a specific period of time. Data is input into both systems, and the output generated by the new system is compared with the equivalent output from the old system. Parallel operation changeover involves a lower risk which makes it beneficial to use it. if the new system does not work correctly, the company can use the old system as a backup until appropriate changes are made.

Parallel operation also has some costs. It is the most costly changeover method, because both the old and the new systems are in full operation, the company pays for both systems during the parallel period. Second disadvantage associated with this changeover method is that parallel operation may not be practical to use if the old system and the new system are not compatible technically. Parallel operation can also be inappropriate when two systems perform different functions or if the new system involves a new method of business operations.

Pilot Operation:
The pilot operation changeover method involves implementing the complete new system at a selected location of the company. A new sales reporting system, for instance, might be implemented in only one branch office, or a new payroll system might be installed in only one department. In these examples, the group that uses the new system first is called the pilot site. During the pilot operation, the old system continues to operate for the entire organization, including the pilot site. Therefore, the pilot operation is a combination of parallel operation and the direct cutover methods.

This changeover approach is less expensive then the parallel operation method and involves less risk of system failure. Also the period for changeover can be much shorter if the system proves successful at the pilot site.

Phased Operation:
This changeover method allows implementing the new system in stages or modules. This method combines the direct cutover and parallel operation to reduce risks and costs. In this method, a part of the system is given to all users. The advantage of choosing the phased operation method is that the risk of errors or failures is limited to the implemented module only. It is also less expensive than full parallel operation because only one part of the system can be worked with at a time. The disadvantage of using this method is that, if the system involves a large number of separate phases, phased operation can cost more than a pilot approach.


References:
Shelly, G.B; Cashman, T.J and Rosenblatt, H.J. (2006), "System Analysis and Design", Thomson, Sixth Edition.