More advanced primers introduce via IF/THEN/ELSE/ENDIF constructs and the COND parameter on the EXEC statement. For example: //STEP2 EXEC PGM=ANALYSE, COND=(4,LT,STEP1) This tells MVS to skip STEP2 if the return code from STEP1 is greater than or equal to 4. This built-in logic gate allows JCL to handle errors gracefully without human intervention—a radical concept in the 1970s that still underpins modern "fail fast" pipelines.
//SYSIN DD * HELLO, WORLD /*
A standard JCL statement follows a specific syntax: //NAME OPERATION OPERAND COMMENTS . Every job consists of three essential statement types: the mvs jcl primer pdf