XCF
Cross-system coupling facility: the part of z/OS that lets the systems in a sysplex talk to each other and know which of them are working.
Also written cross-system coupling facility, couple dataset, XCF signalling
XCF stands for cross-system coupling facility. Despite the name, it is not hardware. It is a component of z/OS, and it is what turns separate systems into a sysplex.
It does three main things. It carries messages between systems, so a program on one system can send data to its partner on another. It keeps track of groups and members: for example, all the DB2 subsystems in one data sharing group. And it watches each system's status, which every system updates regularly.
If a system stops updating its status, XCF notices. The site's policy then decides what happens, which is usually to remove the failed system from the sysplex so the others can take over its work safely.
XCF keeps its own information in couple datasets, which every system in the sysplex shares. You rarely deal with XCF directly, but its messages appear in the system log, and it is behind much of what makes a sysplex reliable.
Where can I learn this hands-on?
Right here, at ZedBank. You take a junior job at a simulated bank and learn each part of the work by doing it, with Zed beside you. There's nothing to install.
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- SysplexA group of mainframe systems joined together so they behave as one, sharing work and data so that no single failure stops the service.
- Coupling facilityA special LPAR that holds shared information for all the systems in a sysplex, so they can work on the same data at the same time.
- LPARA logical partition: one physical mainframe carved into several independent virtual machines, each running its own operating system.
- z/OSThe main operating system that runs on IBM mainframes, in the same way Windows or Linux runs on a laptop or server.
- ENQAn enqueue: the way z/OS reserves a resource, such as a dataset, so two pieces of work do not change it at the same time.