The Data Migration Planner

Help me plan a data migration for this system change safely.

The migration: [FROM WHAT, TO WHAT, ROUGHLY HOW MUCH DATA]
The risks: [DOWNTIME TOLERANCE, DATA QUALITY, CUTOVER]

Provide:
1. The migration steps in sequence (extract, clean, map, load, validate,
   cut over)
2. The data-quality and mapping issues to expect and resolve first
3. How to validate that migrated data is correct and complete
4. The cutover approach (big-bang vs phased vs parallel run) and the
   trade-offs
5. The rollback plan if it goes wrong

Emphasise validation and a fallback — botched migrations are a top cause of
system-change disasters. Flag where technical expertise is essential.