IBM Z Application Modernization with Bob

95% of ATM swaps, 80% of credit card transactions — IBM Z runs them. The problem isn’t that the code doesn’t work. It’s that the people who wrote it are retiring, and the codebases are essentially undocumented.

Bob on Z reads COBOL (including REDEFINES and nested PERFORM), parses JCL job streams, generates zUnit test stubs, and helps define z/OS Connect API wrappers to expose mainframe logic as REST endpoints. The lab in this repo walks through each step on a realistic workload.

The approach: strangler fig. Don’t replace. Wrap. Add tests. Expose APIs. Migrate individual services based on business priority.