Identify What the Old System Really Does
Document users, reports, interfaces, scheduled jobs, manual workarounds and business rules that may not exist in formal specifications.
Map Dependencies
Include databases, files, external partners, devices, identity services, finance processes and downstream reports.
Decide What to Retain
Separate essential business behaviour from historical limitations. Rebuilding every old function can reproduce unnecessary complexity.
Plan Migration and Rollback
Define data cleansing, reconciliation, parallel operation, cutover approval, support coverage and rollback criteria.
Detailed Assessment Checklist
- Business functions and users by criticality
- Interfaces, scheduled jobs, reports and devices
- Data volumes, quality, retention and audit needs
- Known incidents, workarounds and unsupported components
- Source code, build procedure, licences and administrator access
- Business periods when cutover risk is unacceptable
Warning Signs
- Only technical staff are consulted and users are excluded
- The replacement scope copies every old feature without challenge
- Undocumented reports or interfaces are discovered late
- Historical data treatment is postponed until cutover
- No rollback or parallel-run decision is made
- The old environment is left active indefinitely after migration
A Practical Action Sequence
Inventory
Create one view of applications, data, interfaces and owners.
Recover
Capture rules and exceptions from users, code and operations.
Prioritise
Define essential outcomes and remove obsolete behaviour.
Rehearse
Test migration, reconciliation, cutover and rollback.
Retire
Archive required evidence and decommission old components.
Measures Worth Tracking
Use a small set of measures that reflect the business objective. Avoid collecting metrics that nobody will act on.
Management Questions
- What would stop the business if it failed?
- Which knowledge exists only in people’s memory?
- Which external parties must participate in testing?
- What historical information must remain accessible?
- Who authorises final removal of the old system?