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A risk-reducing rollout method where the new system runs concurrently with the legacy system to validate functionality and data reconciliation.
Parallel run is a migration and rollout technique where the new system operates alongside the legacy system for a defined period to validate functionality and data reconciliation. It reduces outage risk and provides controlled fallback options. Coordination effort and operational overhead increase with system complexity.
Percentage of transactions that differ between systems.
Time until all critical checks run without discrepancies.
Additional person-days and costs for running in parallel.
A new ERP was initially run in parallel to correct posting and reporting discrepancies.
Bank ran a parallel operation for weeks to ensure transaction consistency.
Product data and order flows were validated in parallel before decommissioning the old system.
Assess: Identify affected components, data flows and stakeholders.
Plan: Define duration, rollback criteria, test cases and responsibilities.
Prepare: Set up replication, monitoring and reporting.
Execute: Start parallel run, perform comparison tests and validations.
Decide: Based on metrics perform cutover or extend/rollback.