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JES is job entry subsystem on IBM large computers.

If one does not want to implement a program on such a computer interactively and in the background, then one provides a file in the language JCL. If such a file and/or such a job is thus handed over submitted, at to job entry subsystem, then this has control of the job.

The processing of a job by JES subdivided itself into three parts:

  1. Preprocessing
    In this part the actual file is read and interpreted. Here if a syntax error arises, then the treatment breaks off already here. The moreover one files are allokiert, in addition support of the operator or of the HSM can be necessary.
  2. Processing
    Here the actual steps are implemented and the programs are started.
  3. Post office processing
    That is the "“clearing up phase"” of the job run: No more necessary files will not become deleted, files the exclusive processing blocked were approved again, and the expenditure is printed.

Variants

JES gives it in two variants: JES2 and JES3.

Both do in principle the same, the differences for the user are small.

JES3 offers the possibility of distributing jobs on different computers (Nodes) or job nets to bilden.JES2 however is simpler from the configuration expenditure to handle, why operators usually seize with individual computers to JES2.

JES2

JES2 is job entry subsystem in the version 2. JES2 is simpler to furnish than JES3, can for it the advantages of Clustern not use.

There is however the possibility of instructing JES2 it is to let a job on a certain system run. That happens with the following record:

/*JOBPARM SYSAFF=system

JES3

JES3 offers more possibilities as a check of jobs, is substantially higher for it from the configuration expenditure than JES2. The feature absolutely are probably job nets.

A record, independently of // *NET, which is described more near with the job nets, is here mentioned:

// *MAIN ORG=dst, CLASS=class, SYSTEM=system

The individual parameters here are:

  • ORG=dst: The Destination, which corresponds to the expenditure address. Here can one determined, of the computing centre pre-defined, values to register, on which the expenditure is to take place. ORG=LOCAL about the printer could be in the computing centre.
  • CLASS=class: Here the indication of a job class is possible, which helps the operators to arrange jobs. This class hardly differs from the JCL parameter CLASS, however the possibility exists of indicating several indications instead of only one.
  • SYSTEM=system: Hereby the system can be selected, on which the job is to run. The use of this parameter is to be advised against (except in really justified exceptional cases), since one deals the abilities of JES3 to distribute jobs on different systems with it.

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