parallelrunning

Parallel running is a transition strategy in which an organization operates both the existing system and a newly implemented system concurrently for a defined period. The objective is to compare outputs, validate data, and ensure that the new system behaves correctly before decommissioning the legacy system.

It is commonly used during software or ERP implementations, data migrations, and regulatory or policy changes. In taxation, public finance, or government programs, a parallel run helps verify that the new rules or calculations would produce equivalent results to the current system, reducing the risk of errors after cutover.

The approach requires careful planning: define scope and duration, select critical processes or transactions, align master data, configure interfaces, and implement reconciliation mechanisms and monitoring. Stakeholders establish cutover criteria and governance, and staff receive training to operate both systems during the test period.

Benefits include reduced risk, early detection of issues, improved data quality, and a smoother transition for users. Drawbacks include higher cost, duplicated effort, potential confusion among users, and the challenge of keeping two systems synchronized during the interim.

Best practices include limiting the scope to essential functions, performing thorough data reconciliation, automating tests where possible, and establishing a phased or time-bound end date. A detailed cutover plan, issue-tracking, and clear ownership are critical to success.

Alternatives to parallel running include direct cutover (big bang) or phased rollout. See also: cutover, big bang, phased rollout, data migration.