Which changeover method involves running both systems simultaneously for a period?

The parallel changeover method is characterized by the operation of both the old and new systems at the same time for a certain period. This approach allows users and management to compare outputs from both systems, ensuring that the new system is functioning correctly before fully transitioning. It provides a safety net, as any issues with the new system can be addressed while still relying on the old system for operational needs. This method minimizes risks associated with shifting entirely to a new system without adequate testing and validation, which is particularly beneficial in complex environments where reliability is critical.

In contrast, other methods such as direct changeover involve switching from the old system to the new system immediately, leaving no room for a fallback if problems arise. Phased changeovers introduce the new system in stages, which might not offer the same degree of immediate comparison between the systems. The pilot method tests the new system in a limited environment before a full rollout, lacking the simultaneous operation characteristic of the parallel method. Thus, the emphasis on running both systems concurrently is what distinctly defines the parallel changeover method.