COBOL Std 7 Error Handling

7. Error Handling

7.1 Return-Code Standard

All programs and DAL interfaces use the following result-code scheme via DAL-RESULT / SESSION-RESULT / UI-RESULT:

Code	Meaning	Required Action
0	Success	Continue processing.
1	Error — recoverable	Log message; set result; return to caller for decision.
2	End-of-data / not found	Handle gracefully; this is not an error condition.
3	Warning — processing continued	Log warning; continue.
8	Fatal error — terminate	Log; disconnect DB; PERFORM Z000-PROGRAM-END.
16	System error — abend	Emergency disconnect; STOP RUN with non-zero RETURN-CODE.

Note — the pgcobol project uses only codes 0, 1, and 9/99 (EOF). Adopting the full scheme above provides finer-grained diagnostics and removes the ambiguity between error and end-of-data.

7.2 Mandatory Error Paragraph — E000-HANDLE-ERROR

Every program must implement an E000-HANDLE-ERROR paragraph:

<syntaxhighlight lang="cobol">

      E000-HANDLE-ERROR.
          MOVE 'E000-HANDLE-ERROR' TO ERR-PARAGRAPH
          MOVE ERR-MESSAGE         TO UI-SCREEN-MESSAGE
          MOVE 'log-message'       TO UI-METHODS
          CALL 'programui'         USING PROGRAM-UI
          IF ERR-SEVERITY > 4
              PERFORM Z000-PROGRAM-END
          END-IF.

</syntaxhighlight>

7.3 Prohibited Patterns

Prohibited Pattern	Reason / Compliant Alternative
STOP RUN without DB disconnect	Leaves open transactions; always PERFORM Z000-PROGRAM-END first.
Ignoring SQLCODE after any EXEC SQL	Silent failures corrupt data; always EVALUATE SQLCODE.
NEXT SENTENCE (post-COBOL 85)	Ambiguous scope; use CONTINUE inside a scoped IF / EVALUATE.
Empty WHEN OTHER with no comment	Add at minimum: *-- no action required because <reason>
GO TO (except structured exit)	Use PERFORM, EVALUATE, EXIT PARAGRAPH, EXIT PROGRAM.
ALTER statement	Prohibited entirely; dynamic paragraph modification is untestable.
SELECT * in EXEC SQL	Always name columns; column-order changes silently break host-variable binding.

7.4 Cleanup Always Attempted

Termination paragraphs (Z000-series) must always be performed before program exit, regardless of whether prior steps succeeded. This guarantees that database connections and print files are always closed. Guard with conditional logic inside Z000 rather than skipping Z000 itself.

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