Understanding COND=(0,NE) in JCL

 The COND parameter is often one of the most confusing JCL concepts for beginners because its logic works in a somewhat counterintuitive way.

When you code COND=(0,NE) on a job step, the condition is evaluated against the return codes of all previous steps.

If any previous step returns a code other than 0, the condition (0,NE) evaluates to true, and the current step is bypassed (FLUSHED).

If all previous steps return 0, the condition evaluates to false, and the current step executes normally.

 In simple terms, COND=(0,NE) means "Execute this step only if all preceding steps completed successfully with RC=0."

Example

//STEP1    EXEC PGM=IDCAMS

//SYSPRINT DD SYSOUT=

//SYSIN    DD

  SET MAXCC=4

//*

//STEP2    EXEC PGM=IEFBR14

//*

//STEP3    EXEC PGM=IEFBR14,COND=(0,NE)

//*

Execution Results : 

 STEP3 is Flushed.

STEP1 ended with RC=04.

Since 04 is not equal to 0, the condition COND=(0,NE) becomes true.

As a result, STEP3 is skipped (FLUSHED).

 Even though STEP2 completed with RC=00, JCL evaluates the condition against all preceding steps, not just the immediately prior step. Because STEP1 returned a non-zero code, STEP3 does not execute.

Key takeaway: COND=(0,NE) is commonly used to ensure a step runs only when all earlier steps have completed successfully with a return code of zero.