Among common conversion strategies (direct, parallel, phased, pilot), which is typically the longest to execute due to running two systems in tandem and reconciling outputs?

Introduction / Context:
Conversion timelines vary widely. Parallel conversion keeps the legacy and new systems live simultaneously for a defined period, requiring duplicate processing, reconciliation, and user support across both environments—usually making it the longest approach.

Given Data / Assumptions:

• Legacy and target systems can both run in production.
• Operational teams have capacity to maintain two paths.
• Exit criteria (accuracy thresholds, stability) determine when parallel ends.

Concept / Approach:
While phased and pilot can extend timelines for scope reasons, parallel almost always stretches duration because every transaction is processed twice and outputs are cross-checked. The added assurance reduces risk but increases time and cost.

Step-by-Step Solution:
Compare definitions and time implications of each conversion method.Identify the one that inherently doubles processing and requires reconciliation.Select “parallel.”

Verification / Alternative check:
Cutover runbooks show extended calendars for parallel execution windows, reconciliation checkpoints, and defect burn-downs—consistent with longer durations.

Why Other Options Are Wrong:
Direct is fastest (big-bang). Pilot limits scope to a subset—time-limited by design. Phased can be long but typically replaces retired parts as it progresses; it does not always require full dual operation for all functions.

Common Pitfalls:
Underestimating the staffing needed for dual operations; failing to automate reconciliations; letting parallel run without clear exit metrics.

Final Answer:
parallel