Explained: RAS on z/OS

A memory chip fails inside a running mainframe. In a typical server, this would be a crash: a blue screen, a kernel panic, an outage. On an IBM Z system, the error is detected, the affected memory is reconstructed from redundant data held elsewhere in the memory subsystem, and the repair is logged. The running workload continues without interruption. No operator is notified. No ticket is opened. The system fixed itself. This is not exceptional be… Read More

Explained: SMF Records

A batch job ran overnight and consumed three times its usual CPU. A CICS transaction that normally completes in 12 milliseconds is suddenly taking 200. A user account was used to access a sensitive dataset at 3am. A DB2 tablespace is approaching its storage limit. None of these events sent an alert. Nobody was watching at the time. But every one of them left a record. Because on z/OS, almost everything that happens is written down. That writing-do… Read More

Explained: z/OS Connect

A mobile banking app developer needs to display a customer's account summary. The data lives in a CICS COBOL program that has run the bank's core logic for thirty years. The developer knows REST and JSON. She has never heard of CICS, has no idea what a commarea is, and has no intention of learning. She needs an endpoint she can call with a standard HTTP GET request and get back JSON. The CICS web services approach covered in the previous … Read More

Architecture: CICS Web Services

A mortgage application arrives from a bank's customer portal. The portal is a modern React application running on a cloud server. The actual mortgage logic, the eligibility rules, the rate tables, the credit assessment, lives in a COBOL program in a CICS region that has been running, battle-tested, for twenty years. The two systems need to talk. Rewriting the COBOL program is not on the table. Rewriting the portal to speak CICS protocols is n… Read More