Job message queues are created for each job on the system to handle all the message requirements of the job. Job message queues for a single job consist of an external message queue (*EXT) and a set of call message queues.
A call message queue is assigned to each ILE procedure and OPM program that is called within the job. In addition, a job log is created for each job. A job log is a logical queue which maintains all messages sent within a job in chronological order. You may send messages to the *EXT queue or to a call message queue. You do not send messages to the job log. Rather a message sent to either *EXT or a call message queue is also logically added to the job log by the system.