Public sector — North AmericaLegacy to Cloud

They entrusted us with their critical mainframe. We modernized it, transaction by transaction.

Multi-year modernization program of a COBOL application estate on IBM z/OS mainframe. Several critical transactional systems, high volumes. Access cell in co-delivery with a North American prime contractor, under the ATLAS methodology.

Delivery model

Development center (CDR)

Via Vivantro

Typical duration

Multi-year

Team

Multi-stream cell (development, architecture, QA, delivery management)

01Context

COBOL application estate on IBM z/OS mainframe in production for more than two decades
Several critical 24/7 transactional systems
Progressive disappearance of internal COBOL expertise
Requirement of an official discrepancy registry between legacy and target

02Intervention

Existing-system capture: setting a ground truth (screens, reports, transactions, datasets)
Characterization test suite written upstream on the legacy
Pattern-by-pattern migration with line-by-line traceability, accelerated by vibe coding (Claude Code + Copilot)
Parallel runs legacy / target with automatic comparison
Parity audit and discrepancy registry arbitrated by program committee
Capacity building: pair-programming, monthly workshops with client teams