Informix Error -648: Cannot open DEBUG file for SPL routine trace.

Reasons / Common Causes

-648 fires when SET DEBUG FILE TO can't open the specified trace file — per the official guidance, two specific causes: a directory in the specified path doesn't exist, or the directory is write-protected against the group the server runs as.

1. A directory in the specified debug file path doesn't exist, per the official guidance — the most direct cause.
2. The directory exists but isn't writable by the informix group, per the official guidance's specific framing.
3. A relative path resolving differently than expected, landing in a directory that doesn't have the intended permissions, if the debug file name wasn't given as an absolute path.

Solutions / Resolution

1. Check that the directory path is valid, per the official guidance — confirm every directory component in the specified path actually exists.
2. Check that group informix can write to the directory, per the official guidance — correct the directory's group ownership/permissions if needed.
3. Use an absolute path for the debug file name, to avoid ambiguity about which directory a relative path actually resolves to.

Examples

Checking the directory

$ ls -ld /path/to/debug/directory
drwxrwxr-x  ... informix informix ...  /path/to/debug/directory

Confirm the directory exists and group informix has write access.

Setting the debug file with a confirmed-good path

SET DEBUG FILE TO '/path/to/debug/directory/routine_trace.out';

Diagnostic Checks

1. Check that every directory component in the debug file path exists, per the official guidance.
2. Check the directory's permissions for group informix, per the official guidance.

Related Errors / Related Topics

• -649 — "The debug file name must be a NON-NULL CHAR or VARCHAR." A related SET DEBUG error, about the argument's type rather than the path's validity/permissions.

Two specific named causes — a nonexistent directory in the path, or a directory not writable by group informix.