JCL is a set of control statements that provide the specifications necessary to process a JOB. It is the interface between the requirements or instructions in your program and the MVS operating system. Every JOB has three basic JCL statements which are namely:
- JOB
- EXEC
- DD
Without JCL the program will not run on IBM MAINFRAME. So it is like heart of a mainframe.
JCL statement namely the JOB statement. The JOB statement identifies a JOB which is a batch unit of work, to MVS. The JOB statement names the JOB and supplies the necessary information to indicate which resources the JOB will use. A JOB is considered to consist of multiple JOB steps. Each step is made up of an EXEC statement and one or more DD Statements. A JOB is all the JCL statements between a JOB statement and the next JOB statement or null (‘// ‘) statement.
The basic JCL statements.
JOB – Identifies a job and supplies accounting information.
EXEC – A job step by indicating the name of the program to be executed
DD – Identifies a data set to be allocated for the job step.
Comment (//*) – Provides comments.
Null(//) – Marks the end of a job
Delimiter(/*) – Marks the end of an instream data set
OUTPUT – Supplies options for sysout processing
PROC – Marks the beginning of a procedure
PEND – Marks the end of a procedure
JCLLIB – Identifies a private procedure library
INCLUDE – Copies statements from another library member into the job
SET – Sets default values for symbolic variables
IF/THEN/ELSE/END-IF - Provides conditional execution of a job step
COMMAND – Identifies an MVS or JES command that is to be issued when the the job runs.
Each job control statement is further subdivided into 5 fields. They are,
Identifier field
Name field
Operation field
Parameter field
Comment field
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