Data Migration Done Right: Cleansing and Moving Decades of ERP History

Of all the workstreams in an ERP modernization program, data migration is the one most consistently underestimated. It is easy to see why. Moving data appears to be a technical exercise of extraction, transformation, and loading. In practice, it is a business exercise that exposes every inconsistency, duplicate, and undocumented convention that has accumulated over decades. Programs that treat it as an afterthought routinely encounter delays in the final months before go-live.

Decide What to Move

The first decision is scope. Not all historical data needs to move into the new system. Master data, such as customers, suppliers, materials, and the chart of accounts, must be migrated and should be cleansed first. Open transactions, including outstanding orders, open invoices, and inventory balances, must also move. Historical transactions are another matter. Many organizations migrate only a limited period of history, perhaps two or three years, and retain older records in an archive that remains accessible for reporting and audit.

This decision has substantial cost implications. Each additional year of history increases migration effort, testing, and the risk of carrying old problems into the new environment.

Cleanse Before You Move

Data cleansing should begin months before migration. Duplicate customer and supplier records should be identified and merged. Obsolete materials should be retired. Inconsistent units of measure, addresses, and classification codes should be standardized. Business owners, not only IT staff, must participate, because many cleansing decisions require judgment about which record is correct.

Establishing data quality rules and measuring compliance against them provides an objective view of readiness and highlights where effort is still required.

Rehearse Repeatedly

Successful programs conduct several full migration rehearsals, known as mock loads, before the final cutover. Each rehearsal is followed by reconciliation, comparing record counts, balances, and samples between source and target. Rehearsals reveal transformation errors, timing problems, and missing mappings while there is still time to correct them. By the final load, the process should be routine.

Reconcile and Sign Off

The final migration must be reconciled formally, with business owners signing off that balances and key records are correct. Financial balances in particular should be reconciled to the penny. This sign-off provides assurance to auditors and leadership that the new system begins from an accurate position.

The Bottom Line

Data migration is a business undertaking with technical components, not the reverse. Programs that decide scope early, cleanse data well in advance, rehearse migrations repeatedly, and require formal reconciliation will go live with data they can trust. The effort is considerable, but it determines whether the new system earns user confidence from the first day. A clean start is also the foundation for analytics and AI initiatives that depend on reliable information.