Interrupting

The z/OS® Communications Server provides a mechanism for a terminal in receive mode to tell its partner that it would like to send. This is the signal data flow in Communications Server, which is detected on the next SEND, RECEIVE or ISSUE DISCONNECT command from the task.

When a signal flow occurs, CICS® raises the SIGNAL condition and sets EIBSIG in the EIB. CICS default action for the SIGNAL condition is to ignore it. For the signal to have any effect, the task must first detect the signal and then honor it by changing the direction of the conversation.

On a 3270 display terminal and some others, the ATTENTION key is the one that generates the interrupt. Not all terminals have this feature, however, and in z/OS Communications Server, the bind image must indicate support for it as well, or the z/OS Communications Server ignores the interrupts.