Informix Error -479

Reasons / Common Causes

-479 fires when DESCRIBE is executed against a descriptor that wasn't allocated enough occurrence slots to hold every column the target statement/table actually returns — the descriptor's WITH MAX occurrence count (see -470) is too small.

1. A descriptor allocated with a fixed, hardcoded occurrence count that's smaller than the actual number of columns in the query being described.
2. A query that grew over time (columns added), while the descriptor allocation size wasn't correspondingly increased.
3. Generic/dynamic SQL tooling assuming a small, fixed maximum column count that doesn't hold for every possible query it might need to describe.

Solutions / Resolution

1. Use ALLOCATE DESCRIPTOR to increase the occurrence value, per the official guidance, then retry the DESCRIBE statement.
2. For dynamic/generic tooling, allocate the descriptor generously or determine the required size dynamically before allocating, rather than assuming a small fixed maximum.
3. If the query grew over time, review the descriptor allocation size alongside any schema/ query changes that add columns.

Examples

Increasing the allocated occurrence count

ALLOCATE DESCRIPTOR 'desc1' WITH MAX 50;
PREPARE stmt1 FROM 'SELECT * FROM wide_table';
DESCRIBE stmt1 USING SQL DESCRIPTOR 'desc1';

The disallowed insufficient allocation

ALLOCATE DESCRIPTOR 'desc1' WITH MAX 5;
PREPARE stmt1 FROM 'SELECT * FROM wide_table';  -- has 20 columns
DESCRIBE stmt1 USING SQL DESCRIPTOR 'desc1';
-- -479: wide_table has more columns than desc1 can hold

Diagnostic Checks

1. Compare the descriptor's allocated occurrence count against the actual number of columns in the statement being described.
2. Check for a recent schema/query change that added columns, if a previously-working DESCRIBE started failing.

Related Errors / Related Topics

• -470 — "The value of occurrence must be greater than 0." A related occurrence-value restriction, about the value being positive rather than sufficiently large.
• -472 — "Occurrence value is out of range." A related occurrence-indexing error, at access time rather than at DESCRIBE time.

Allocate the descriptor generously, or determine the actual column count dynamically before allocating, rather than assuming a small fixed maximum will always be sufficient.