Task control blocks (TCBs)

A task control block (TCB) represents a z/OS® task. A running CICS® system is a z/OS address space containing multiple TCBs and hence multiple z/OS tasks. Within CICS, a CICS task itself runs on a TCB.

A TCB is a dispatchable unit of work in z/OS. The z/OS dispatcher dispatches TCBs. The CICS dispatcher dispatches CICS tasks to run on TCBs.