JCL - Overview

When to use JCL

JCL is used in a mainframe environment to act as a communication between a program (Example: COBOL, Assembler or PL/I) and the operating system. In a mainframe environment, programs can be executed in batch and online mode.

JCL - Environment Setup

Installing JCL on Windows/Linux

There are many Free Mainframe Emulators available for Windows which can be used to write and learn sample JCLs.
One such emulator is Hercules, which can be easily installed in Windows by following few simple steps given below:

JCL - JOB Statement

JOB Statement is the first control statement in a JCL. This gives the identity of the job to the Operating System (OS), in the spool and in the scheduler. The parameters in the JOB statement help the Operating Systems in allocating the right scheduler, required CPU time and issuing notifications to the user.

JCL - EXEC Statement

Each JCL can be made of many job steps. Each job step can execute a program directly or can call a procedure, which in turn executes one or more programs (job steps). The statement, which holds the job step program/procedure information is the EXEC statement.

JCL - DD Statement

Datasets are mainframe files with records organised in a specific format. Datasets are stored on the Direct Access Storage Device (DASD) or Tapes of the mainframe and are basic data storage areas. If these data are required to be used/created in a batch program, then the file (i.e., dataset) physical name along with the file format and organisation are coded in a JCL.

JCL - Base Library

Base Library is the Partitioned Dataset (PDS), which holds the load modules of the program to be executed in the JCL or the catalogued procedure, which is called in the program. Base libraries can be specified for the whole JCL in a JOBLIB library or for a particular job step in a STEPLIB statement.

JCL - Procedures

The JCL Procedures are set of statements inside a JCL grouped together to perform a particular function. Usually, the fixed part of the JCL is coded in a procedure. The varying part of the Job is coded within the JCL.

JCL - Conditional Processing

The Job Entry System uses two approaches to perform conditional processing in a JCL. When a job completes, a return code is set based on the status of execution. The return code can be a number between 0 (successful execution) to 4095 (non-zero shows error condition). The most common conventional values are:

JCL - Defining Datasets

A dataset name specifies the name of a file and it is denoted by DSN in JCL. The DSN parameter refers to the physical dataset name of a newly created or existing dataset. The DSN value can be made up of sub-names each of 1 to 8 characters length, separated by periods and of total length of 44 characters

Input-Output Methods

Any batch program executed through a JCL requires data input, which is processed and an output is created. There are different methods of feeding input to the program and writing output received from a JCL. In batch mode, there is no user interaction required but input and output devices and required organisation are defined in JCL and submitted.

Running COBOL Programs using JCL

Compiling COBOL Programs

In order to execute a COBOL program in batch mode using JCL, the program needs to be compiled and a load module is created with all the sub-programs. The JCL uses the load module and not the actual program at the time of execution.

JCL - Utility Programs

IBM Dataset Utilities

Utility programs are pre-written programs, widely used in mainframes by system programmers and application developers to achieve day-to-day requirements, organising and maintaining data. A few of them are listed below with their functionality:

JCL - Basic Sort Tricks

The day-to-day application requirements in a corporate world that can be achieved using Utility Programs are illustrated below:

JCL Questions and Answers

JCL Questions and Answers has been designed with a special intention of helping students and professionals preparing for various Certification Exams and Job Interviews. This section provides a useful collection of sample Interview Questions and Multiple Choice Questions (MCQs) and their answers with appropriate explanations.

JCL - Quick Guide

JCL - Overview

When to use JCL

JCL is used in a mainframe environment to act as a communication between a program (Example: COBOL, Assembler or PL/I) and the operating system. In a mainframe environment, programs can be executed in batch and online mode.

JCL - Useful Resources

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Discuss JCL

Job Control Language (JCL) is the command language of Multiple Virtual Storage (MVS), which is the commonly used Operating System in the IBM Mainframe computers. JCL identifies the program to be executed, the inputs that are required and location of the input/output and informs the Operating System through Job control Statements. In mainframe environment, programs can be executed in batch and online modes. JCL is used for submitting a program for execution in batch mode.