Mainframes remain critical for powering essential business applications. However, understanding how transactions flow and components communicate can be challenging. This session provides an overview of typical mainframe architectures, walking through common transaction flows within z/OS. We’ll examine the interactions between subsystems like CICS, IMS, and associated components, explaining how they work together to ensure speed, reliability, and scalability. You'll gain insights into the movement of data through message queues, network pathways, and attachment facilities. Whether you’re an architect, developer, or operations professional, this session will solidify your foundational understanding of mainframe connectivity and transaction processing, providing a practical basis for improved system management.