Job Entry Subsystem (JES) is a subsystem of the OS/390 and MVS mainframe operating systems that manages jobs (units of work) that the system does. Each job is described to the operating system by system administrators or other users in job control language (JCL). The operating system then sends the job to the JES program. The JES program receives the job, performs the job based on priority, and then purges the job from the system.
There are two versions, JES2 and JES3. JES3 allows central control of the processing of jobs using a common work queue. Both OS/390 and MVS provide an interactive menu for initiating and managing jobs.