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Job Control Language Introduction

JCL Introduction:

Job control language (JCL) is a set of statements that you code to tell the z/OS operating system about the work you want it to perform.

Understanding JCL:

To get the MVS system(Multiple Virtual Storage, more commonly called MVS, is the most commonly used operating system on mainframe) to do work for us, we must describe the system the work we want and the resources we need and we use Job Control Language (JCL) to provide this information.

Job Control Language (JCL) is a language that directs the Operating systems in the handling of application programs.

JCL is a mean of communication between an application program and the computers operating system (MVS).

It is a set of control statements that provide the specifications necessary to process a JOB.

  • Job: Execution of one or more related programs in sequence.

  • Job step: Each program to be executed by a job.

What JCL does?

JCL used to communicate with the O.S. about your requirements for running a job.

  • Telling O.S. who you are (allows priority distinctions).

  • Telling O.S. your space and time requirements.

  • Telling O.S. what programs (load modules) you need

  • Telling O.S. what data sets are needed by program(s)

What can be done with JCL?

  1. Submit a job to the operating system.

  2. Request resources needed to run the job.

  3. Control the systems processing of the job.

  4. You can pass parameter values through JCL to application program using PARM parameter in EXEC statement.

What is a Job?

A job is defined as execution of one or more related programs in a sequence. It provides the communication between an application program(Example: COBOL, Assembler or PL/I) and the computers operating system.

Job flow :

During execution a job goes through the following phases:

  1. Input

  2. Conversion

  3. Execution

  4. Output

Video Tutorial: JCL Introduction



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