Informix Error -651

Reasons / Common Causes

-651 fires when a VARCHAR(m, r) column definition's reserved width r is greater than its maximum width m — per the official guidance, the reserved size (the space pre-allocated in the row) can't exceed the column's actual maximum size.

1. The two numbers in VARCHAR(m, r) transposed or mistyped, per the official guidance's suggested first check — r ending up larger than m by mistake.
2. A genuine attempt to reserve more space than the column's maximum, misunderstanding what the reserved-size parameter does — it pre-allocates space within the maximum, not beyond it.

Solutions / Resolution

1. Check the punctuation of the column definition, per the official guidance, for a transposed or mistyped number.
2. Revise the statement so m is greater than or equal to r, per the official guidance — the maximum width must be at least as large as the reserved width.

Examples

The disallowed combination

CREATE TABLE orders (order_id INT, notes VARCHAR(50, 100));
-- -651: reserved size 100 exceeds maximum size 50

Corrected

CREATE TABLE orders (order_id INT, notes VARCHAR(100, 50));

Diagnostic Checks

1. Compare the two numbers in the VARCHAR(m, r) definition directly, confirming m >= r.

Related Errors / Related Topics

• -650 — "Maximum varchar size has been exceeded." A related VARCHAR-definition error, about the maximum width itself exceeding 255, rather than the reserved width exceeding the maximum.

A straightforward numeric-order check — confirm the maximum width (m) is at least as large as the reserved width (r).