Informix Error -631

Reasons / Common Causes

-631 fires when creating an optical cluster (the Optical Subsystem's mechanism for grouping simple-large-object data for storage on optical media) names a column that isn't TEXT/BYTE — per the official guidance, optical clusters can only be created on columns of these two types.

1. The optical cluster statement naming a column of a type other than TEXT/BYTE — the direct, only cause.
2. A column-naming mistake, per the official guidance's suggested check — confirm the column is actually the one intended, and review the table's definition.

Solutions / Resolution

1. Check that the column is the one you meant to specify, per the official guidance.
2. Review the table's definition to confirm the intended column's actual declared type:

   SELECT colname, coltype FROM syscolumns
   WHERE tabid = (SELECT tabid FROM systables WHERE tabname = 'documents');
   

3. Only attempt to create the optical cluster on a genuinely TEXT/BYTE column — there's no supported way to create one on a column of a different type.

Examples

A column-type mismatch

-- doc_id is INT, not TEXT/BYTE
-- an optical cluster statement naming doc_id would fail with -631

Confirming the correct column and its type

SELECT colname, coltype FROM syscolumns
WHERE tabid = (SELECT tabid FROM systables WHERE tabname = 'documents');

Diagnostic Checks

1. Query syscolumns for the target column's actual declared type, confirming it's TEXT/BYTE before attempting to create the optical cluster.

Related Errors / Related Topics

• -632 — "Cannot create optical cluster." A related optical-cluster-creation failure, for a different underlying reason once the column type itself is correct.
• -633 — "Cannot drop optical cluster." The corresponding drop-side failure.

A column-type mismatch specific to the Optical Subsystem — confirm the target column is actually TEXT/BYTE via syscolumns before retrying.