ZCOM Subsystem
ZCOM Concepts
The driver is then responsible for handling the message. Messages on the express queue are sent before those on the high priority queue which are sent before those on the low priority queue.
Because the ZCOM Subsystem itself takes responsibility for the delivery of messages, the sending program is able to specify a number of options when it passes the message to the system. These options include:
•Continue execution whether the message is sent successfully or not.
•Continue execution but report any error status (status messages are queued to the ZLU of the calling program).
•Continue execution; a definite response will be queued to the program ZLU when the send has completed.
•Suspend execution until the send has completed (i.e., acknowledgment that the message was transmitted).
On completion, the message buffer may also be passed back to the sending application program if required.
Each message on the ZLU has a ‘type’ attribute so that the program reading the ZLU is able to differentiate between status messages, timeout messages and data messages from terminals or other programs.
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