Job class
A single-character label on a job that tells the system what kind of work it is and how to schedule it.
Also written CLASS
Job class is a letter or digit on the JOB statement that groups work of a similar kind so the system can schedule it sensibly.
Sites define what each class means, and the definitions typically reflect resource limits and expectations. One class might be for short test jobs allowed to run immediately with a tight time limit. Another might be for long production work restricted to overnight hours. Another might be limited to a small number running at once because the work is heavy.
This is how a system stops a single large job from blocking dozens of small ones, and how a site keeps development work from consuming the resources production needs.
Practically, you use the class your site tells you to use for the kind of work you are doing. Choosing wrongly usually shows up as a job that sits in the queue and never seems to start, or one that is cancelled for exceeding a limit you did not know applied.
Output classes work the same way, controlling what happens to what the job prints.
Related terms
- JOB statementThe first statement in every job, giving it a name and telling the system who is running it and how to treat it.
- JES2The job entry subsystem: the part of z/OS that queues jobs, decides when they run, and collects their output.
- JobA unit of batch work submitted to the system, made up of one or more steps that run in order.
- SYSOUTOutput sent to the spool rather than to a dataset, where you can read it after the job finishes.
- SubmitHanding JCL to the system to be run, which queues it as a job and gives it a job number.