Moving data off a legacy system is where modernization projects succeed or stall. The new platform can be ready on time and still sit unused because nobody trusts the data in it.
This is the plan I follow, built from migrations in financial regulation and healthcare data.
The phases
- Profile the source data before you design anything
- Map the fields and the business rules
- Run trial migrations early and often
- Validate with the people who use the data every day
- Plan the cutover and the rollback