Job Message Queues

A message queue exists for every call stack entry within each job. This message queue facilitates the sending and receiving of informational messages and exception messages between the programs and procedures running on the call stack. The message queue is referred to as the call message queue.

The call message queue is identified by the name of the OPM program or ILE procedure that is on the call stack. The procedure name or program name can be used to specify the target call stack entry for the message that you send. Because ILE procedure names are not unique, the ILE module name and ILE program or service program name can optionally be specified. When the same program or procedure has multiple call stack entries, the nearest call message queue is used.

In addition to the call message queues, each job contains one external message queue. All programs and procedures running within the job can send and receive messages between an interactive job and the workstation user by using this queue.

For information about sending and receiving exception messages by using APIs, see the Message Handling APIs in the API topic collection of the Programming category in the IBM® i Information Center.