Job control language (JCL) is the set of statements that tells IBM z/OS what work to run and which resources that work needs. In a typical batch job, the core statements are JOB, EXEC, and DD: they identify the job, specify a program or procedure to run, and connect its steps to input, output, or other resources.
What job control language does
JCL describes work for the operating system rather than performing the application’s processing itself. It specifies what program or procedure should run, where its input can be found, and how its output or other resources are to be handled. The program named in the JCL performs the application work; z/OS uses the JCL to organize and run that work.
JCL is commonly encountered in IBM mainframe batch processing. IBM notes that the statement set is extensive, although most jobs use a comparatively small subset. Application programmers generally need some familiarity with JCL; production control analysts often need deeper proficiency to create, monitor, correct, and rerun batch workloads. IBM’s overview of JCL explains its purpose and typical users.
How JOB, EXEC, and DD fit together
A useful first reading of a JCL listing is to look for its job, the steps it runs, and the resources each step uses.
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- JOB identifies the unit of work and can carry information that applies to the job as a whole.
- EXEC names the program or procedure to run and begins a job step. A job can contain multiple EXEC statements, with each one defining a step.
- DD, short for data definition, connects a data set or another input/output resource to a name used by a program or procedure in a particular step.
In simplified terms, JOB labels the job, EXEC describes its steps, and DD supplies the resource definitions those steps use. These statements are the foundation for understanding many listings, not a complete account of JCL syntax. IBM summarizes the basic JCL concepts and the role of the EXEC statement.
Independent reader supportYour contribution helps us test, update, and keep practical guides available for everyone.What a basic JCL explanation leaves out
Real jobs can use additional statements, parameters, procedures, and conventions that depend on the workload and environment. The JOB–EXEC–DD sequence is a teaching model for recognizing the main parts; it should not be treated as a universal template or a complete syntax guide.
For exact statement syntax and the full statement inventory, consult IBM’s z/OS 3.1 JCL statement reference. That reference is specific to z/OS 3.1, so check the documentation for the operating-system version and environment you use when troubleshooting or writing JCL.
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