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Q: What is the difference between COND and IF/THEN/ELSE in JCL?
Answer:
COND Parameter:
- Tests return codes from previous steps
- Bypasses step if condition is TRUE
- Works opposite to programming logic!
- COND=(4,LT) means: Skip if 4 < any previous RC
IF/THEN/ELSE:
- More intuitive programming-like syntax
- Executes steps when condition is TRUE
- Supports AND, OR operators
- Can check ABEND conditions
Example:
// Using COND (skip if RC < 4) //STEP2 EXEC PGM=PROG2,COND=(4,LT) // Using IF/THEN/ELSE // IF STEP1.RC = 0 THEN //STEP2 EXEC PGM=PROG2 // ELSE //ERROR EXEC PGM=ERRPROC // ENDIF
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Q: What is the difference between COND and IF/THEN/ELSE?
Answer:
COND tests return codes to skip steps (negative logic - skips IF true). IF/THEN/ELSE tests conditions to execute steps (positive logic). IF supports complex expressions, COND is simpler but confusing. IF preferred for readability. COND on JOB affects all steps; on EXEC affects that step.
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Q: How to pass data between steps?
Answer:
Use DISP=PASS to pass datasets. Receiving step references same DSN. Or use symbolic parameters. GDG allows relative references (+1 created, 0 passed). Temporary datasets (&& prefix) auto-pass. SYSIN instream data copied to subsequent steps.
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Q: What is REGION parameter?
Answer:
REGION specifies memory limit. REGION=0M means no limit (use system default). REGION=4M limits to 4MB. On JOB card affects all steps, on EXEC affects that step. Below 16M line: REGION=2048K. Modern systems often use REGION=0M.
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Q: How to use //IF statement?
Answer:
//IF (condition) THEN executes following steps if true. Conditions: RC, ABEND, ABENDCC, RUN, STEP.RC. Example: //IF (STEP1.RC = 0) THEN ... //ENDIF. Can nest. ELSE available. Clearer than COND parameter.
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Q: What is STEPLIB vs JOBLIB?
Answer:
JOBLIB at job level provides program libraries for all steps. STEPLIB at step level overrides JOBLIB for that step. STEPLIB takes precedence. Both searched before LINKLIST. Multiple libraries concatenated. DDN must be STEPLIB/JOBLIB exactly.
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Q: How to define temporary dataset?
Answer:
Temporary datasets: DSN=&&TEMP or omit DSN. Exist for job duration only. Not cataloged. Passed between steps with DISP=PASS. Automatically deleted at job end. Example: //WORK DD DSN=&&TEMP,UNIT=SYSDA,SPACE=(CYL,5)
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Q: How to use IDCAMS conditionally?
Answer:
IF LASTCC/MAXCC condition THEN command. Example: IF MAXCC < 8 THEN REPRO... SET MAXCC/LASTCC resets codes. Allows conditional processing in IDCAMS job steps.
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Q: Explain RESTART parameter
Answer:
RESTART=stepname restarts job at specified step. RESTART=(stepname,checkid) for checkpointed restart. Use after abend to continue from failure point. Prior steps skipped. Data must be recoverable or recreatable.