Abstract

This paper explores running Java microservices on IBM z/OS using the embedded CICS Liberty runtime. By leveraging the tight integration between CICS Transaction Server and Liberty—a lightweight, modular Java EE application server—enterprises can modernize incrementally without discarding proven COBOL and PL/I assets.
The paper walks through Liberty’s JVM architecture within CICS, outlines step-by-step implementation of a hybrid Java-COBOL application, and evaluates deployment strategies, monitoring tools, and operational best practices. It also highlights key features, real-world challenges, and design considerations for maintaining high performance and reliability. The goal is to equip mainframe development and operations teams with the technical depth to adopt and scale Java workloads on z/OS confidently.