Data migration reconciliation
Record counts alone are not reconciliation. They are the first line of a document that most programmes never finish writing.
Why counts are not enough
Counts reconcile long before values do. A migration can land every record and still move the debtors book by millions, because the damage lives in amounts, currencies, signs and relationships, none of which a row count can see. The reconciliation question is not simply how many records arrived. It is whether the business received its data, provably.
What reconciliation must prove
- Completeness
- Everything in scope arrived, and everything out of scope demonstrably did not.
- Control totals
- Financial and quantity totals agree between source and target, at the level the business balances its books.
- Values
- Amounts, balances and quantities match record by record, not just in aggregate.
- Relationships
- The customer still owns its open items. The material still belongs to its plants. Referential meaning survived.
- Transformation
- Where values were deliberately changed, the change matches the agreed rule, and the rule is documented.
- Rejected records
- Every rejection is listed, explained and dispositioned. Silence is not a disposition.
- Duplicates and exceptions
- Merged and exceptional records are accounted for individually, with their survivorship decisions.
- Business outcomes
- The processes that depend on the data actually run: invoicing, payments, picking, reporting.
- Sign-off
- A named owner accepted the evidence, and the evidence was readable without a data engineer interpreting it.
The chain, not the checkpoint
Reconciliation is a chain that runs the length of the migration, not a checkpoint at the end. Evidence is captured as data leaves the source, as transformation changes it, and as the target accepts it. Exceptions feed remediation, and remediation triggers re-proof, because a fix that is not re-reconciled is just a newer assumption.
Designed this way, reconciliation becomes cheap to repeat. That matters, because migration cycles repeat, and evidence that cannot keep up with the cycles gets abandoned exactly when it is needed most. On our retail programme, every one of 11 go-lives produced a reconciliation pack the business signed, and the 450-store weekend was signed off the same way, at full volume.
The audience decides the format. Reconciliation evidence is written for the named business owner who signs it, which is why our packs read like statements, not query output. A sign-off from someone who cannot read the evidence is theatre, and auditors know it.
Source
Baseline captured at extraction
Transformation
Deliberate change, evidenced
Target
Accepted and accounted for
Reconciliation
Counts, totals, values, relationships
Exception
Listed, explained, owned
Remediation
Fixed at the cause
Re-proof
Reconciled again, not assumed