Preparing data for migration to a new system

Data migration is often the riskiest part of replacing a system. A structured approach keeps it under control.

1. Inventory the data

List every data set in the old system, its volume and whether it is needed in the new one.

2. Decide what moves

Active records usually migrate; old history may be archived and kept available read-only.

3. Clean the data

Remove duplicates, fix formats and fill mandatory fields before migration — not after.

4. Map fields

Document how each old field maps to the new system, including value conversions.

5. Run trial migrations

1. Migrate into a test environment.
2. Check counts and totals against the old system.
3. Let users review samples.
4. Fix and repeat.

6. Plan the cut-over

Freeze changes in the old system, run the final migration, reconcile and switch.

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