Management Information › System Overview Display › Job Entry Subsystem

Job Entry Subsystem

Besides verifying the current version of z/OS in use on the computer, the CA Auditor System Overview Display also identifies the job entry subsystem (JES) used and the date and time of the latest initial program load (IPL). Data centers can use JES2 or JES3. Each of these job entry subsystems performs basically the same functions in a z/OS system. That is, both JES2 and JES3 manage jobs from the moment they are read into the system until the job output is purged.

In an environment with more than one processor, JES2 functions somewhat differently. Each JES2 processor is independent of the others, even though they can share common spool files. JES3, on the other hand, introduces centralized control over all its processors, selecting work from a common job queue. Because a steady flow of enhancements in the last few years has reduced the major differences between the two systems, there is little reason to switch to the other version of JES if the data center is satisfied with the performance of the JES it uses. See the “Job Information” chapter for more information about job entry subsystems.