Uncovering the seams in Mainframes for Incremental Modernisation

Mainframe systems continue to run much of the world's computing workload, but it's often difficult to add new features to support growing business needs. Furthermore the architectural challenges that make them slow to enhance also make them hard to replace. To reduce the risk involved, we use an incremental approach to legacy displacement, gradually replacing legacy capabilities with implementations in modern technology. This strategy requires us to introduce seams into the mainframe system: points in which we could divert logic flow into newer services. In a recent project Alessio Ferri and Tom Coggrave investigated several approaches to introduce these seams into a long-lived mainframe system.