Informix Error -644: FAMILY(), VOLUME(), and DESCR() require BLOB column on optical medium.

Reasons / Common Causes

-644 fires when FAMILY(), VOLUME(), or DESCR() is called on an argument that isn't a TEXT/BYTE column stored on optical media — per the official guidance, these three functions specifically require a BLOB column on optical medium, the same underlying type/medium requirements as -631/-638 but for a function call rather than CREATE OPTICAL CLUSTER.

1. FAMILY()/VOLUME()/DESCR() called on a column of a different data type, per the official guidance.
2. FAMILY()/VOLUME()/DESCR() called on a TEXT/BYTE column stored in an ordinary storage space rather than on optical media, per the official guidance — the same optical-vs-ordinary-storage distinction as -638.

Solutions / Resolution

1. Check that the argument isn't a column of a different data type, per the official guidance.
2. Check that the argument isn't a TEXT/BYTE column stored in an ordinary storage space, per the official guidance, rather than on optical media.
3. Confirm the column's storage space and type before calling any of these three functions on it, the same check used for -638.

Examples

The disallowed attempt

SELECT FAMILY(order_id) FROM orders;
-- -644: order_id is INT, not a BLOB column on optical media

A BLOB column on the wrong storage medium

-- content is TEXT, but stored in an ordinary blobspace, not optical media
SELECT VOLUME(content) FROM documents;
-- -644: content isn't on optical media

Diagnostic Checks

1. Confirm the argument's declared type is TEXT/BYTE, and that its storage space is optical media, the same two checks used for -638.

Related Errors / Related Topics

• -631 — "Cannot create optical cluster on column that is not TEXT or BYTE." Same underlying type requirement, in the CREATE OPTICAL CLUSTER context.
• -638 — "Cannot cluster TEXT or BYTE columns on non-optical media." Same underlying optical-media requirement, in the CREATE OPTICAL CLUSTER context.

The same type/medium requirements as -631/-638, applied to FAMILY()/VOLUME()/DESCR() function calls instead of CREATE OPTICAL CLUSTER.