---
title: Secure data migration and cutover
description: "Data migration is the riskiest moment of an HRIS project: a bad transfer and January's payroll is wrong for 500 people. Our 3-wave method (sandbox, parallel run, cutover) secures this critical step. - **Reading time**5 min - **Level**Advanced - **Last…"
url: "https://illizeo.com/en/centre-aide/secure-data-migration-and-cutover/"
updated: "2026-09-21"
category: Consulting
---

# Secure data migration and cutover

Data migration is the riskiest moment of an HRIS project: a bad transfer and January's payroll is wrong for 500 people. Our 3-wave method (sandbox, parallel run, cutover) secures this critical step.

- **Reading time**5 min
- **Level**Advanced
- **Last updated**May 2026
- **Module**Deployment support

## Data to migrate

| Category | Typical volume | Sensitivity |
| --- | --- | --- |
| Employee profiles | 1 line / person | Very high |
| Active contracts | 1-2 / person | Very high |
| Leave balances | 1 per absence type | High |
| Historical payslips | 12-60 / person | High |
| Signed documents | 5-50 / person | Medium |
| Past reviews | 1-5 / person | Medium |

## Step-by-step (3 waves)

1. ### Wave 1 - Sandbox (weeks 1-3)

   Import into a test tenant. Validation on 10-20 typical cases. Identify format gaps, null values, encodings.
2. ### Wave 2 - Pre-prod (weeks 4-6)

   Full import in pre-production. Consistency tests: totals, counts, qualitative sampling. Reconciliation with old system.
3. ### Wave 3 - Production with parallel run (weeks 7-10)

   Production import. Month M processed in parallel in old and new system. Line-by-line comparison.
4. ### Official cutover

   Cutover date announced. Old system goes read-only. New system becomes single source.
5. ### Hypercare (4 weeks)

   Reinforced support after cutover: Illizeo team + in-house team on 24/5 hotline during first month.

## FAQ

   What about ghost data (employees gone 5 years ago)?

Dedicated archive, anonymisation per GDPR policy. No systematic migration.

   What if a gap is found during parallel run?

Joint investigation. Either the source system was wrong, or the import has a bug. Cause is tracked and fixed.

   Cutover window?

Ideally a weekend. Avoids conflict with HR/payroll operations during the week.

   What if cutover fails?

Documented Plan B: rollback to old system, re-import after fix. Always prepared even if never used in practice.

### See User training plan

Learn to train 500 people in 4 weeks.

[See all Consulting articles](/en/centre-aide/?cat=consulting)

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