Informix Error -941: String processing error while evaluating function (function_name).

Reasons / Common Causes

-941 fires when a case-conversion function (such as UPPER/LOWER) encounters an invalid character (single- or multi-byte) in its input string — per the official guidance, this is the specific, named cause.

1. An invalid single-byte character in the input string, per the official guidance.
2. An invalid or malformed multi-byte character in the input string, per the official guidance — plausible on a multi-byte code set where a byte sequence doesn't form a valid character.
3. A code-set/locale mismatch between how the data was actually encoded and how the database session interprets it, producing what looks like an invalid character to the case-conversion function even though the underlying data may be fine in its original encoding.

Solutions / Resolution

1. Verify that the characters in the input string are valid, per the official guidance, for the database's configured code set/locale.
2. Execute the query again, per the official guidance, once the input data is confirmed (or corrected) to contain only valid characters.
3. Check for a code-set/locale mismatch if the data was loaded from a source using a different encoding, since that's a plausible source of apparently-invalid characters.

Examples

Checking a specific row's data for invalid characters

SELECT order_id, LENGTH(status) FROM orders WHERE order_id = 42;
-- inspect the raw data (e.g. via a hex dump at the application level)
-- for byte sequences that don't form valid characters in the database's
-- configured code set

Diagnostic Checks

1. Identify the specific row/value causing the failure, and inspect its raw bytes against the database's configured code set for validity.
2. Check for a code-set/locale mismatch if the data came from an external source.

Related Errors / Related Topics

No closely related error codes are cross-referenced for -941 in this set yet.

An invalid character (often from a code-set/locale mismatch) in the input to a case-conversion function — inspect the specific row's raw bytes against the database's configured code set.