Job Entry Subsystem 2/3

The Job Entry Subsystem ( JES ) is a subsystem under z / OS on IBM mainframes.

In the early days of the IBM mainframe, the so-called batch or batch processing was the only form of data processing. So-called jobs were then coded on punched cards, read in via hole card reader into the system and processed sequentially. Although today no more punch cards are processed, the batch continues to play an important role. Today, it is primarily for automated processing, often for the so-called mass processing used. The control statements for batch processing are then as now encoded in the Job Control Language (JCL ).

The Job Entry Subsystem controls as a subsystem of the operating system z / OS jobs to be executed. It is required by the operating system to accept jobs, work up to dispose, forward them to the operating system for execution and receive the outputs of the job. In short, the JES brings jobs into the operating system and receives the outputs of the jobs.

For z / OS two job entry subsystem exist: JES2 and JES3, where JES2 is the most widespread.

Operation

The processing of a job through the JES is divided into three parts:

Variants

JES is available in two versions: JES2 and JES3.

They both do basically the same thing, the differences are small for the user:

  • JES3 provides the possibility of jobs on different computers to distribute or create job networks ( nodes).
  • JES2 is easier to handle from the configuration effort forth, which is why operators access to individual computers usually to JES2.

JES2

JES2 is the Job Entry Subsystem in version 2

JES2 originated from HASP (Houston Automatic Spool Program), which was developed by IBM in the 1960s for NASA. Even today, writes JES2 its messages as $ HASP messages to system log.

JES2 is easier to set up than JES3, it can not take advantage of clusters.

However, there is the possibility of JES2 should be instructed to leave a job run on a given system. This with the following record:

/ * JOBPARM SYSAFF = system JES3

JES3 is the Job Entry Subsystem in version 3

JES3 provides more options for control of jobs, is it from the configuration effort considerably higher than JES2. The ultimate tool are well- job networks.

A record, regardless of / / * NET, which is described in the job network is mentioned here:

/ / * MAIN ORG = dst, CLASS = class, SYSTEM = system The individual parameters are in this case:

  • ORG = dst: The destination, which is the output address. Here you can specific, from the datacenter enter predefined values ​​on the output should be sent. ORG = LOCAL about could be the printer in the data center.
  • CLASS = class: Here is the specification of a job class is possible, which helps the operators to classify jobs. This class is not very different from the JCL CLASS parameter; However, it is possible to specify multiple characters instead of just one.
  • SYSTEM = system: This system can be selected on which the job should run. From the use of this parameter is (except in really exceptional and justified cases ) not recommended, as you distribute the capabilities of JES3 jobs on different systems to handle it.
  • Mainframe operating system (IBM)
  • Software component
z/OS
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