What is the PRIMARY purpose of performing a parallel run of a now system?

The primary purpose of a parallel run is to validate the new system's processing and outputs by comparing them directly against the results of the legacy system (its predecessor). Both systems are run simultaneously using the same live input data for a defined period. This comparative process ensures the new system is accurate, reliable, and performs as expected before the old system is decommissioned. It serves as a final, real-world validation, minimizing the risk of business disruption during the transition.

A. To train the end users and supporting staff on the new system

While users gain experience during a parallel run, this is a secondary benefit. The primary method for education is dedicated training programs.

B. To verify the new system provides required business functionality

This is too general. While a parallel run does verify functionality, its specific and primary purpose is the direct comparison and validation against the old system.

C. To reduce the need for additional testing

A parallel run is a form of testing (live validation) and does not replace or reduce the need for earlier phases like unit, integration, or system testing.

1. ISACA CISA Review Manual

27th Edition. Domain 3: Information Systems Acquisition

Development

and Implementation

Section 3.5.4 System Conversion. The manual describes parallel conversion as running the old and new systems simultaneously to compare and verify the new system's results against the old. This direct comparison is the core of the validation process.

2. ISACA

"Glossary of Terms

" (www.isaca.org/glossary). The definition of "Parallel Run" emphasizes the comparison of results between the old and new systems to verify the new system's functionality and accuracy before the old system is discontinued.

3. Valacich

J. S.

& George

J. F. (2020). Modern Systems Analysis and Design (9th ed.). Pearson. Chapter 12

"Designing the User and System-to-System Interfaces

" discusses implementation strategies. It states that parallel installation involves running both the old and new systems concurrently to check that the new system's output is comparable to the old system's

thus validating its performance.