Case Study: Top Multinational Professional Services Firm designs modernization of an 11M‑line 'black‑box' mainframe in under a month with CAST Imaging

Top tier Consultancy designs modernization of a ‘black-box’ core mainframe application in under a month

A top-tier multinational consultancy partnered with a leading North American freight operator that needed a solid business case and multi-year roadmap to modernize a mission‑critical mainframe application. The monolithic “black‑box” system—built over three decades and spliced together through acquisitions—comprised ~11 million lines of code (Natural, Adabas, Cobol, JCL, DB2), 100+ schemas and 7,500 tables, making it difficult to understand, change or justify transformation investments.

The firm ran a focused 12‑week engagement in three phases—prioritization (profiling 21 legacy systems and uncovering core architecture), blueprinting (risk reduction and transitional planning) and operationalization (new operating model)—using CAST Imaging and a customized community extension to reverse‑engineer interdependencies and Adabas schemas. The work produced a six‑month roadmap and first iteration, clarified design rationale, improved Opex/Capex planning, reduced risk, and boosted stakeholder confidence—leading the client to adopt CAST Imaging for the broader modernization program.