Fixed length columns are awkward to use with variable byte character sets. The reason is that ANSI SQL treats fixed length strings in terms of characters, while most applications treat fixed length strings in terms of physical bytes. The difference cannot be reconciled.
Teradata SQL addresses this problem by treating LATIN, UNICODE, and GRAPHIC character data type columns according to ANSI, but also providing the export width rules to export these data type columns as fixed byte length fields. For more information about export width, see Working with Export Widths.