Chapter 39: Legacy System Maintenance and Modernization -- Further Reading

Books

"Working Effectively with Legacy Code" by Michael C. Feathers This is the definitive guide to working with code you did not write and do not fully understand. Feathers provides techniques for getting legacy code under test, breaking dependencies, and making safe changes. While the examples use Java and C++, the concepts -- characterization tests, seam identification, dependency breaking -- apply directly to COBOL legacy maintenance. Essential reading for any programmer who maintains systems built by others. Available through major online booksellers.

"Refactoring: Improving the Design of Existing Code" by Martin Fowler Fowler's catalog of refactoring techniques provides systematic approaches for improving code structure without changing behavior. The techniques for extracting methods, replacing conditionals with polymorphism, and introducing explaining variables have direct COBOL analogs (extracting paragraphs, replacing nested IFs with EVALUATE, using 88-level condition names). Available through major online booksellers.

"Modernizing Legacy Applications in the Cloud" by Robert Stackowiak This book addresses the strategic and technical challenges of moving legacy systems to cloud environments. It covers assessment methodologies, migration patterns (rehost, replatform, refactor, replace), data modernization, and the organizational change management required for successful modernization. Directly relevant to COBOL-to-cloud migration planning. Available through major online booksellers.

Online Resources

IBM Developer: "Modernizing COBOL Applications" IBM's developer resources include a collection of articles, tutorials, and reference architectures for modernizing COBOL applications on z/OS. Topics include API enablement with z/OS Connect, database modernization from VSAM to DB2, DevOps for mainframe, and hybrid cloud integration. The practical, IBM-specific guidance complements the language-neutral strategies presented in this chapter. Available on the IBM Developer website.

Micro Focus: "Application Modernization" Micro Focus publishes extensive resources on modernizing COBOL applications, including migration from mainframe to distributed platforms, code analysis tools, automated refactoring, and integration with modern DevOps toolchains. Their perspectives on COBOL modernization outside the z/OS environment are valuable for organizations considering platform migration. Available on the Micro Focus website.

Martin Fowler's "StranglerFigApplication" Article Fowler's original article defining the Strangler Fig pattern for incremental legacy system replacement is essential reading for modernization architects. The pattern describes how to build new functionality around the edges of an existing system, gradually replacing it without requiring a big-bang cutover. Available on Martin Fowler's website (martinfowler.com).

IBM Documentation

IBM Redbook: "Modernizing Applications with IBM CICS" This Redbook covers modernization strategies specifically for CICS-based COBOL applications, including RESTful API exposure, event-driven architecture with CICS Events, and integration with Liberty containers. It provides detailed technical guidance for the most common COBOL modernization scenarios. Search for this title on the IBM Redbooks website.

IBM Redbook: "DevOps for the Mainframe" Modern maintenance and modernization require modern development processes. This Redbook covers how to bring DevOps practices -- version control with Git, automated testing, continuous integration, continuous delivery -- to mainframe COBOL development. Understanding these practices is essential for sustainable modernization. Available on the IBM Redbooks website.

IBM Application Discovery and Delivery Intelligence (ADDI) IBM's ADDI tool provides automated code analysis, dependency mapping, and impact analysis for COBOL applications. The documentation covers how to use ADDI to understand legacy codebases, trace data flows, identify dead code, and plan modernization efforts. Available on the IBM Documentation portal.

Standards and Industry Guidance

Gartner Research: "Application Modernization Strategy" Gartner publishes research on application modernization strategies, decision frameworks (the "7 Rs" of modernization: retain, retire, rehost, replatform, refactor, rearchitect, replace), and best practices for managing modernization programs. While requiring a Gartner subscription, the frameworks are widely referenced in modernization planning. Available through Gartner.

The Open Group: "IT4IT Reference Architecture" The IT4IT reference architecture provides a framework for managing the IT value chain, including application lifecycle management, change management, and service management. Understanding IT4IT helps COBOL programmers align their modernization work with enterprise IT governance. Available through The Open Group website.

"The Phoenix Project" by Gene Kim, Kevin Behr, and George Spafford This novel-format book illustrates DevOps principles through the story of a fictional company struggling with legacy IT systems and troubled deployments. While not COBOL-specific, the lessons about flow, feedback, and continuous improvement apply directly to the challenge of modernizing and maintaining COBOL systems. Available through major online booksellers.