the field, on one page
Mainframe Modernization
Sixty years of business logic. One disciplined way out.
The problem
Beneath every bank, insurer, and government hums an estate the cloud never reached — business rules written in COBOL, maintained by a retiring generation, blocking every ERP, cloud, and AI program stacked on top of it.
The menu — and the trap
The 7 Rs (retain, retire, rehost, replatform, refactor, rearchitect, replace) are options, not a strategy. Programs fail by picking one for the whole estate. The discipline: decide per application, on evidence.
The meter
The cost of staying is MIPS, MLC, and scarce people; the cost of leaving is dominated by understanding, verification, and the parallel run. Dead code — typically 33–40% of an estate — is the cheapest scope you will ever cut.
The standard
Trustworthy modernization is evidence-led: every extracted rule traceable to its source line (lineage), every output identical across runs (determinism). If a vendor cannot show both, keep walking.
~95% rule extraction on palmbench · vs ~30% generic llms · 33–40% dead-code dividend