Job Control Language (JCL) is a scripting language used to control and manage batch jobs on IBM mainframe computers. It was first introduced in the early 1960s and has since become an essential part of mainframe computing. In this beginner's guide, we will explore what JCL is, how to write it, and its best applications.
What is JCL?
JCL is a scripting language that is used to control and manage batch jobs on IBM mainframe computers. Batch jobs are groups of programs that are run sequentially without any user interaction. JCL is used to define the parameters of these jobs, including the input and output files, the processing options, and the resources required for the job.
JCL programs are written in a simple text format and are compiled into an executable format that is run on the mainframe computer. The JCL compiler is part of the IBM mainframe operating system and is responsible for translating the JCL code into machine language.
How to write JCL
JCL programs are made up of statements that define the various parameters of the batch job. Here is a simple example of a JCL program:
//JOBNAME JOB (ACCT#),'YOUR NAME',CLASS=A,MSGCLASS=X,MSGLEVEL=(1,1)
//STEP1 EXEC PGM=YOURPGM
//SYSPRINT DD SYSOUT=*
//SYSOUT DD SYSOUT=*
//SYSIN DD *
YOUR INPUT DATA GOES HERE
/*
This JCL program has two steps. The first step defines the parameters of the job, including the account number, job name, job class, message class, and message level. The second step specifies the program that will be run (YOURPGM) and the input and output files that will be used.
The syntax of JCL statements is similar to that of other programming languages, with each statement beginning with a keyword that identifies the type of statement (such as JOB or EXEC) and followed by parameters that define the specific details of the statement.
Best Applications for JCL
JCL is commonly used in mainframe computing to manage batch jobs, particularly in industries such as finance, banking, and insurance. It is used to automate routine tasks, such as processing customer transactions, generating reports, and performing backups.
JCL is particularly useful for managing large-scale batch processing tasks, as it allows multiple programs to be run sequentially without any user intervention. It is also useful for managing the resources required for batch processing, such as memory and disk space.
Conclusion
In conclusion, JCL is an essential part of mainframe computing and is widely used in industries such as finance, banking, and insurance to manage batch processing tasks. JCL programs are written in a simple text format and are compiled into an executable format that is run on the mainframe computer. By following the basic syntax of JCL statements, users can define the parameters of their batch jobs and automate routine tasks with ease.