Which implementation approach allows users to run both old and new systems simultaneously?

The approach that allows users to run both old and new systems simultaneously is known as parallel running. This method is particularly useful in situations where a new system is being implemented, as it minimizes risk while ensuring that users can continue their operations without disruption. In parallel running, the old system and the new system operate side by side for a specific period. This allows users to familiarize themselves with the new system and provides an opportunity to validate that the new system functions correctly and meets the necessary requirements.

Furthermore, should any issues arise with the new system, users can revert to the old system without any significant impact on their processes, ensuring continuity and reliability during the transition period. This method is often preferred for critical systems where the consequences of failure would be significant.

Other approaches, like pilot and phased implementations, do not provide the same level of immediate fallback option as parallel running. In pilot implementations, the new system is tested in a limited capacity, while phased implementations roll out the new system in stages, which may not allow for simultaneous operations across the entire organization. Direct changeover, on the other hand, replaces the old system with the new one all at once, presenting higher risks during the transition.