Conversion from one computer system to another can be accomplished by several methods. A parallel conversion is one in which both the old and new computer systems are operated simultaneously. This is usually done to keep the old system available as a backup until the new system is working satisfactorily. Parallel conversion boasts some advantages, but it also has some drawbacks as well.

Running Two Systems Simultaneously

Running two systems in parallel demands twice the resources to accomplish the same work as a single system. This demands more electricity and increases operating costs. Workers must also perform twice their normal work load in order to achieve the same output, essentially entering or changing data twice for every one time they would do so on a single system to ensure that information remains identical between both. The doubled workload slows production, which raises the cost of the final product by diminishing the workers' potential output per paid period of work.

Probability of Errors

Input errors are always a possibility, but when the amount of data being input doubles, the probability of an error increases with it. The likelihood of errors may also increase if workers are compelled to work faster, and an input error on one system will take it out of synchronization with the other. When this happens, the systems are no longer parallel, and further time and energy must be invested to track and correct the erroneous entry.

Advantages of Parallel Conversion

While parallel conversion does have some disadvantages, its primary appeal is in the potential for continued smooth operations during the changeover period. The new system can be run alongside the old system for weeks or months, allowing the discovery of any problems in the new system without exposing the business to a shutdown when problems occur. This feature is especially useful when adopting new untested systems or systems that may require unforeseen specialization and optimization after implementation.

Alternative Conversion Strategies

In addition to parallel conversion, several other conversion strategies exist. An abrupt cutover, also known as a plunge, involves shutting down the old system and converting to the new one at a predetermined time. Abrupt conversions are typically scheduled during extended periods of down time, such as weekends or the beginning of a new financial year, in order to discover and correct any potential problems before workers return and begin using the new system. A location conversion occurs when several locations use the same system. One location becomes a test site for the new system and, when the problems are worked out there, the system is implemented at all other locations as well. A staged conversion involves implementation of updates or a new system in stages, with each stage being debugged before the next is implemented.