Informix Error -682: Error reading constraint index on table table-name.

Reasons / Common Causes

-682 is flagged by the official text as an internal error: the server was unable to validate a constraint because it couldn't read the index implementing it — per the official guidance, the accompanying ISAM error carries the specific reason, and this is part of the same general family of constraint-index-related internal errors as -622.

1. An underlying ISAM-level error while reading the constraint's index, per the official guidance's pointer to checking the accompanying ISAM error — the only documented path to the specific cause.
2. System-catalog or root dbspace corruption affecting the index, similar to the plausible causes named for -622's related "locating" failure, though -682's own official text doesn't explicitly name this.

Solutions / Resolution

1. Check the accompanying ISAM error code, per the official guidance — the only documented path to the specific underlying cause.
2. Have the database server administrator check for system-catalog or root dbspace corruption, using the same diagnostic path as -620/-622 (oncheck/onutil/tbcheck), given the similarity to those related errors.
3. If this recurs, note all circumstances and contact IBM Informix Technical Support, per the official guidance.

Examples

Checking for catalog/root dbspace corruption

$ oncheck -cc
-- or the platform-appropriate equivalent, given the constraint-index read failure

Diagnostic Checks

1. Check the accompanying ISAM error code first, per the official guidance.
2. Run a catalog/root dbspace consistency check, given the similarity to -622's framing.

Related Errors / Related Topics

• -679 — "Cannot read constraint violation data for constraint constraint-name." A related internal constraint-error, about violation diagnostic data rather than the index itself.
• -680 — "Cannot write constraint violation data for constraint constraint-name." Same family, write-side.
• -622 — "Error on locating constraint index index-name." A closely related internal error — also about a constraint's index being unreadable/unlocatable, in the specific context of a uniqueness check during row insert/update rather than general constraint validation.

Closely related to -622 — same diagnostic path (accompanying ISAM error, then a catalog/root dbspace consistency check).