Part IV: Messaging and Integration

"Every enterprise system that survives past version 1.0 eventually needs to talk to something else. The question isn't whether you'll need messaging and APIs — it's whether you'll design them intentionally or discover them accidentally in a production incident."

What This Part Covers

Part IV connects your COBOL systems to everything else. Four chapters cover IBM MQ for transactional messaging, event-driven architecture patterns, API-first design with z/OS Connect, and data integration patterns that bridge mainframe and distributed worlds.

This is where the mainframe stops being an island. Modern enterprise architecture demands that COBOL services participate in event-driven workflows, expose RESTful APIs for mobile and web consumers, and exchange data reliably with cloud-based systems. These chapters teach you how to do that without sacrificing the reliability and transactional integrity that make the mainframe the system of record in the first place.

SecureFirst Retail Bank's mobile modernization project — wrapping COBOL behind APIs while maintaining five-nines on the core — is the primary example throughout this part. Continental National Bank's MQ-based inter-system messaging provides the enterprise messaging patterns.

Chapters in This Part

Chapter	Title	Key Question
19	IBM MQ for COBOL	How do you implement transactional messaging from COBOL?
20	Event-Driven Architecture	How do MQ triggers and CICS events enable reactive systems?
21	API-First COBOL	How do you expose mainframe services as modern APIs?
22	Data Integration Patterns	What patterns work for mainframe-to-distributed data exchange?

Progressive Project

You'll add the messaging and integration layer to your HA banking system: MQ queues for inter-system communication, event-driven notifications for fraud detection, REST APIs for the mobile banking channel, and data integration feeds to the data warehouse and regulatory reporting systems.

Prerequisites

Part I (Chapter 1). Part III Chapter 13 (for CICS integration). Basic understanding of TCP/IP networking.