CICS transaction
One unit of online work in CICS: the whole exchange of receiving a request, doing the work, and sending a response.
Also written transaction
A transaction in CICS is a single piece of online work. Someone types an identifier or presses a key, CICS starts the associated program, that program does its work and sends a response, and the transaction ends.
Two properties define it. It is short, measured in milliseconds, because thousands of others are waiting. And it is atomic where data is concerned: the changes it makes are committed together at the end, or backed out entirely if something fails. Money never leaves one account without arriving in the other.
The program does its work through CICS commands: read from a screen, read a record, update a database, write to a queue, send a screen back. Between transactions, CICS holds nothing on the program's behalf unless explicitly asked to.
Because they are so short and so numerous, transactions are also the unit of measurement for the whole system. Capacity, licensing, performance targets and service levels are all expressed in transactions per second and response time per transaction.
Related terms
- CICSThe transaction manager that runs online mainframe applications, and the software behind a great many screens bank staff use.
- Transaction IDA four-character code that tells CICS which program to run, typed on the screen or triggered by a key.
- Pseudo-conversationalThe CICS programming style where a program ends after sending each screen, rather than waiting for the user to reply.
- Commit and rollbackMaking a set of changes permanent together, or undoing them together, so a transaction never half-happens.
- Online transaction processingHandling many small pieces of work in real time while someone waits: a card payment, a balance check, a seat booking.