Information Systems

Job Control Language or JCL is a set of control statements that provide the specifications necessary to process a job. Communication with the OS is by typing commands or Job Control Language statements.
Role of JCL
We do not use JCL to write computer programs. Instead, it consists of control statements that introduce a computer job to the operating system, provide accounting information, direct the operating system on what is to be done, request hardware devices, and execute the job.
JCL tells the operating system everything it needs to know about a job’s (I/O) requirements. We code the JECL (Job Entry Control Language) to specify on which network computer to run the job, when to run the job, where to send the resulting output. IBM provides two job entry systems for Z/Os: JES2 for decentralized control and JES3 for highly centralized control of several computers.
Purpose of using JCL
JCL functions are
• Identifies users which is essential for security
• Identify programs
• Specify device requirements
• Run-time intervention
There are 3 basic JCL statements in every job – JOB, EXEC, and DD. The first statement in every job is a JOB statement to furnish necessary data to identify the job. EXEC statement has to be coded to indicate the name of the program to be executed. Within each step, DD statements have to be coded for every file that is to be processed by the program
Format:
Identifier[name][operation][operand][comments]