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Claude for Mainframe

For enterprise engineering teams that need their modern developers to work safely with legacy mainframe systems

5–8 MonthsInstructor-led Workshop
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Program Overview

What This Program Covers

This multi-month program equips existing Java and Python developers with the skills, workflows, and Claude-based tooling required to read, document, modify, and modernize legacy mainframe systems — without becoming career COBOL developers. Designed for enterprise engineering teams facing the well-documented shortage of mainframe specialists, this program demystifies z/OS, COBOL, JCL, and the surrounding ecosystem while establishing safe, auditable workflows for using Claude as a legacy-code comprehension and modification partner. The program multiplies the reach of remaining mainframe SMEs — extending their supervisory capacity across a larger cohort of modern developers rather than replacing them.

What You'll Learn

  1. 1Understand mainframe architecture (z/OS, datasets, JCL, DB2/IMS) and how it differs from modern distributed systems
  2. 2Read and interpret COBOL programs, JCL, and batch flows using Claude as a comprehension tool
  3. 3Document undocumented legacy systems to audit-ready standards and capture institutional knowledge from retiring experts
  4. 4Draft and validate modifications to COBOL programs using a disciplined draft-review-test cycle
  5. 5Design integration patterns that bridge mainframe systems to modern Java and Python applications
  6. 6Evaluate modernization approaches (rehost, refactor, rewrite, replace) and execute selective modernization projects
  7. 7Extend the reach of remaining mainframe SMEs by enabling modern developers to work independently on routine tasks

Outline

Program Snapshot

AI Foundational Module — Claude for Enterprise Developers

  • ›What Claude is and how it differs from other AI assistants
  • ›Prompt engineering essentials for enterprise developers
  • ›Context management: giving Claude the right information without leaking sensitive data
  • ›Enterprise Claude deployment models: API tier, Zero Data Retention, VPC/on-prem options
  • ›Claude Code installation, workspace setup, and daily-driver workflows

Path 1 — Mainframe Ecosystem for Modern Developers

  • ›z/OS fundamentals: hardware, LPARs, address spaces, TSO/ISPF navigation
  • ›Dataset types: sequential, PDS, PDSE, VSAM — and the EBCDIC vs ASCII gotchas
  • ›JCL essentials: JOB, EXEC, and DD statements — the syntax that runs everything
  • ›DB2 on z/OS, IMS, and IDMS for the modern developer
  • ›Security, RACF, and mainframe change management culture

Path 2 — Claude for Legacy Code Work

  • ›Claude chat vs Claude Code for legacy work — when to use each
  • ›Context management across multi-thousand-line COBOL programs
  • ›Prompt patterns for legacy code: explain-this, find-side-effects, map-dependencies, extract-business-rules
  • ›The verification loop: how to catch what Claude gets wrong on COBOL

Path 3 — Reading, Documenting, and Understanding

  • ›COBOL fundamentals for modern developers: structure, data types, core verbs
  • ›Deep COBOL reading with Claude: section-by-section analysis of complex programs
  • ›Dependency mapping across entire codebases with Claude Code
  • ›Business rule extraction: reverse-engineering intent from implementation
  • ›JCL, batch flows, and ABEND error interpretation
  • ›Documentation and structured knowledge capture from retiring SMEs

Path 4 — Modifying and Interacting

  • ›The draft-review-test cycle: developer as author, Claude as drafter, SME as reviewer
  • ›Generating COBOL modifications safely: COPY books, REDEFINES, level-88 conditions
  • ›JCL and batch modifications with production-safe testing
  • ›Test generation and regression harnesses for COBOL programs
  • ›Cross-language interop: calling mainframe programs from Java and Python via Zowe
  • ›Working with mainframe data from modern tooling: EBCDIC conversion, packed decimal

Path 5 — Modernization Patterns (Optional Extension)

  • ›The modernization decision framework: rehost, refactor, rewrite, replace
  • ›API wrapping legacy code: exposing REST/GraphQL to modern consumers
  • ›Data extract and sync patterns: mainframe-as-source-of-truth architecture
  • ›The strangler fig pattern with Claude: incremental replacement strategy
  • ›Selective refactoring: moving batch jobs to Java or Python with rollback plans
  • ›Full COBOL-to-Java conversion using Claude Code with equivalence testing
  • ›When NOT to modernize: making the honest case to stay

Capstone Project

  • ›Cohort teams of 3–5 learners select a real legacy system to augment or modernize
  • ›Teams execute the full workflow: comprehension, documentation, modification
  • ›Ongoing SME participation for review and sign-off throughout
  • ›Final presentation of findings and recommendations to organizational leadership
  • ›Deliverables: documented legacy system, executed change, and next-steps roadmap

Who This Is For

  • Java and Python software engineers who need to work with legacy mainframe systems
  • Technical leaders managing teams that support both mainframe and modern application portfolios
  • Business analysts and architects who need to understand mainframe behavior without becoming COBOL experts
  • Enterprise organizations facing mainframe SME retirement and knowledge drain

Prerequisites

  • Solid Java or Python programming experience and comfort with REST APIs
  • Comfort with command-line tools and version control (git)
  • Read-only access to the target mainframe environment provisioned before Path 2 begins
  • At least one active mainframe SME available to the cohort for review and sign-off
  • Enterprise Claude accounts will be provisioned per learner — no prior COBOL experience required

Bring This Program to Your Team

Every bILTup program is fully customized to your team's tech stack, goals, and timeline. Tell us about your team and we'll design something built specifically for you.

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