Informix Error -687: Set debug file before tracing SPL routines.

Cause and resolution

Set debug file before tracing SPL routines.

A TRACE statement was executed before a SET DEBUG FILE statement. The destination of the output of the TRACE statement is unknown. This error can also apply to the TRACE OFF statement.

Example of error:

TRACE procedure; -- error

Correction:

SET DEBUG FILE TO 'trace.out'; TRACE procedure;

Oninit® Troubleshooting Guidance

Reasons / Common Causes

-687 fires when TRACE (or TRACE OFF) is executed before SET DEBUG FILE TO — per the official guidance, TRACE's output has no destination until a debug file has been set.

TRACE procedure_name executed with no prior SET DEBUG FILE TO, per the official guidance's own example — the direct, common cause.
TRACE OFF executed without ever having set a debug file in the session, per the official guidance's note that this applies to TRACE OFF too.
SET DEBUG FILE TO executed in a different session/connection than the one issuing TRACE — the debug file setting is session-scoped, so setting it elsewhere doesn't help this session.

Solutions / Resolution

Issue SET DEBUG FILE TO before TRACE, per the official guidance's documented correction:
```
SET DEBUG FILE TO 'trace.out';
TRACE procedure_name;
```
Confirm SET DEBUG FILE TO and TRACE run in the same session, if the error persists despite having set a debug file somewhere.

Examples

The disallowed order

TRACE procedure_name;
-- -687: no debug file has been set yet

Corrected

SET DEBUG FILE TO 'trace.out';
TRACE procedure_name;

Diagnostic Checks

Check whether SET DEBUG FILE TO ran earlier in the same session, before the TRACE/ TRACE OFF statement that failed.

Related Errors / Related Topics

-648 — "Cannot open DEBUG file for SPL routine trace." A related SET DEBUG FILE error, about the path's validity once SET DEBUG FILE TO is actually issued.
-649 — "The debug file name must be a NON-NULL CHAR or VARCHAR." A related SET DEBUG FILE error, about the argument's type.

TRACE needs SET DEBUG FILE TO first, in the same session — check the statement order before troubleshooting anything else.