Each of this JCL Statements have a label – a symbolic name assigned to them. Its like naming kids. Well, there could be so many boys in your area, but how do distinguish them? Of course, by their names.
In the same way, a JCL may contain a bunch of DD Statements, one for Input file, one for the output file, one for the error file. How do you tell them apart, by naming them. As a good practice, we always give names to all our JCL Statements. Names kinda help you to refer back to these statements in the future. You want to point out a particular JCL Statement to your friend, just spell out its name.
But, notice carefully, each label(name) is preceded with two slashes //. The two slashes are a JCL Statement’s signature. They indicate that the statement is a JCL Statement(one of JOB, EXEC, DD). Every JCL Statement wear the two slashes //. A naked statement without // won’t be treated as a JCL Statement.
Now, every JOB, EXEC and DD Statement has got these whole lot of parameters. What you’ll be learning throughout these tutorials is mostly the parameters. Parameters add stuff and meaning to the JCL Statement.
Now, let me give you a booster, that’s going to help you organise the way you think about this JCL.
- JCL is made up of mainly JOB, EXEC and DD.
- JOB is easy to learn and use.
- EXEC is easy and fun to use.
- DD Statements take three forms
1. DD Statements to read a file.(easy)
2. DD Statements to write to the logs.(easy)
3. DD Statements to create a new file(hard!); you’d have to learn parameters such as DISP, UNIT, DCB, SPACE and several others to code this.
Have a good look at this chart :