Conditional processing in JCL allows you to control the execution of job steps based on the success or failure of previous steps. This is crucial for creating robust and efficient job streams that can handle various scenarios without manual intervention.

1. Return Codes (RC):

   • Each job step in JCL returns a code upon completion, known as the Return Code (RC).
   • Return codes typically range from 0 to 4095, where 0 usually indicates success, and any non-zero value indicates some form of error or warning.

2. COND Parameter:

   • The COND parameter is used to specify conditions under which a job step should be bypassed.
   • Syntax: COND=(code,operator,stepname)
     • code: The return code to compare against.
     • operator: The comparison operator (e.g., EQ, NE, GT, LT, GE, LE).
     • stepname: The name of the previous step whose return code is being checked.

3. IF/THEN/ELSE/ENDIF Statements:

   • These statements provide a more readable and flexible way to handle conditional processing.
   • Syntax:

     //IF (condition) THEN
     //    [JCL statements]
     //ELSE
     //    [JCL statements]
     //ENDIF
     

• Explanation:
  • STEP2 will be bypassed if STEP1 returns a code less than 4.

• Explanation:
  • If STEP1 completes successfully (RC=0), STEP2 will execute.
  • If STEP1 fails (RC≠0), STEP3 will execute.

Task: Write a JCL script that runs PGM1. If PGM1 completes with a return code of 0, run PGM2. Otherwise, run PGM3.

Solution:

Task: Write a JCL script that runs PGM1 and PGM2. Skip PGM2 if PGM1 returns a code greater than or equal to 8.

Solution:

1. Incorrect Return Code Comparisons:

   • Ensure you are using the correct comparison operators (EQ, NE, GT, LT, GE, LE).

2. Misplaced IF/THEN/ELSE/ENDIF Blocks:

   • Ensure that the IF/THEN/ELSE/ENDIF blocks are correctly nested and properly closed.

3. Overusing COND Parameter:

   • While the COND parameter is useful, overusing it can make the JCL script hard to read. Consider using IF/THEN/ELSE/ENDIF for better readability.

Conditional processing in JCL is a powerful feature that allows you to create dynamic and flexible job streams. By understanding and utilizing return codes, the COND parameter, and IF/THEN/ELSE/ENDIF statements, you can control the flow of your jobs based on the outcomes of previous steps. This ensures that your jobs can handle various scenarios efficiently and effectively.