MRO
Multiregion operation: the way CICS regions connect so that work started in one region can use programs and files in another.
Also written multiregion operation, function shipping, transaction routing, ISC, intersystem communication
MRO, multiregion operation, lets several CICS regions work together as if they were one. Large sites split an application over many regions instead of running everything in one, for capacity, availability and to keep different kinds of work apart.
A common layout has terminal-owning regions, which handle the user's connection, application-owning regions, which run the programs, and sometimes file-owning regions, which own important files. MRO connects them in three main ways. Transaction routing sends a transaction from the region the user is connected to, to a region that runs it. Function shipping sends a request such as a file READ to the region that owns the file. Distributed program link runs a program in another region.
Connections between regions on the same system or sysplex use MRO. Connections to CICS regions on other systems use ISC, intersystem communication, over the network.
Users and programs usually do not notice any of this: a transaction looks the same wherever it runs. It matters when something fails, because the problem may be in a different region from the one the user is connected to.
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- CICS regionOne running copy of CICS, with its own programs, files and users. A site typically runs several.
- LINK and XCTLTwo CICS commands for running another program: LINK runs it and comes back, XCTL hands over and does not come back.
- CICSThe transaction manager that runs online mainframe applications, and the software behind a great many screens bank staff use.
- SysplexA group of mainframe systems joined together so they behave as one, sharing work and data so that no single failure stops the service.
- CICSPlex SMCICSPlex System Manager: IBM software that manages many CICS regions from one place and spreads transactions across them.