AS400 jobs can originate from several sources and are classified by how they originate on the system. In this course, and in general, you will deal mostly with two types of jobs: interactive and batch.
An interactive job begins when a user signs on to an AS400 and it terminates when the user sign off the AS400 or the job is ended. Interactive jobs run in conversational mode, which means there is a dialogue of sorts between the user and the program, utility or operating system function. Because of this conversational, back-and-forth nature of interactive jobs, any CPU-or I/O-intensive request a user makes could lock up the workstation keyboard until the request is completed. Therefore, it is often advisable to direct such requests to a subsystem designed to handle them. That is, to submit them as batch jobs.
Batch jobs can execute without user interaction; they do not require data or controlling values to be input through the workstation once they have started. Batch jobs are sent to a job queue until they can begin execution. A job queue is a staging area, managed by the subsystem in which the job will run, where batch jobs wait in line for their turn at processing. Each batch subsystem can execute only a limited number of batch jobs concurrently. If no other higher-priority jobs are waiting, a batch job can start right away; otherwise, it must wait its turn. Batch jobs may also be held until a certain time of day. For example, a given batch job may be automatically run each night at 11:00 p.m. An example of such a batch job would be the nightly deletion of work files before a system backup.