ASSRANGE - Array Boundary Violation in Production

"Code review scenario: You're reviewing a trainee's COBOL program that loads product pricing into an array:

01  PRICE-TABLE.
    05  PRICE-ENTRY OCCURS 5000 TIMES.
        10  PRODUCT-ID    PIC X(10).
        10  UNIT-PRICE    PIC 9(5)V99 COMP-3.

PROCEDURE DIVISION.
    PERFORM LOAD-PRICES
    PERFORM CALCULATE-TOTALS.

LOAD-PRICES.
    OPEN INPUT PRICE-FILE
    MOVE 1 TO WS-INDEX
    PERFORM UNTIL END-OF-FILE
        READ PRICE-FILE INTO PRICE-ENTRY(WS-INDEX)
        ADD 1 TO WS-INDEX
    END-PERFORM.

Situation:

• Program compiled without SSRANGE, tested with 100 records - worked fine
• Moved to production, ran with 5,200 products
• Program produced incorrect totals (no ABEND)
• Financial reports showed wrong revenue figures
• Discovered after month-end close

Questions:

1. What went wrong?

2. How would SSRANGE have helped?

3. What's the production impact?

4. How do you fix this immediately and long-term?"

• Understanding of subscript checking
• Quality assurance practices
• Production readiness criteria
• Defensive programming techniques

1. Root Cause:

• Program processed 5,200 records but array only holds 5,000
• After WS-INDEX = 5000, records 5,001-5,200 overwrote memory
• Likely corrupted WS-TOTAL or other working storage variables
• No ABEND because memory overwrite was in valid address space
• Garbage values caused incorrect calculations

2. SSRANGE Impact:

• With SSRANGE (or NOSSRANGE for production):
• Program would ABEND immediately at WS-INDEX = 5001
• S0C4 or 0E38 ABEND with subscript error message
• Problem detected immediately, not after month-end

3. Immediate Fix:

LOAD-PRICES.
    OPEN INPUT PRICE-FILE
    MOVE 1 TO WS-INDEX
    PERFORM UNTIL END-OF-FILE OR WS-INDEX > 5000
        READ PRICE-FILE INTO PRICE-ENTRY(WS-INDEX)
        IF WS-INDEX < 5000
            ADD 1 TO WS-INDEX
        ELSE
            DISPLAY 'WARNING: Table overflow at record ' WS-INDEX
            PERFORM WRITE-ERROR-LOG
        END-IF
    END-PERFORM.

4. Long-term Solution:

• Increase table size to 10,000 (allow for growth)
• Or use dynamic table (OCCURS DEPENDING ON)
• Or implement file-based processing (no table limit)
• Establish testing standards: Test with MAX+1 records

5. Process Improvements:

• Always compile with SSRANGE for testing
• Test with boundary conditions (0 records, MAX records, MAX+1 records)
• Code review checklist: Look for array processing
• Add input record count validation

• ❌ Doesn't understand why no ABEND occurred
• ❌ Suggests just increasing array size without bounds checking
• ❌ Doesn't mention testing implications
• ❌ Can't explain difference between compile-time and runtime checking
• ❌ Doesn't recognize this as a critical production issue

• "Why didn't the program ABEND if it accessed invalid subscript?"
• "What's the difference between SSRANGE and NOSSRANGE?"
• "How much overhead does SSRANGE add? Would you use it in production?"
• "What if you need to process unlimited records?"