Translation tables map characters between an extended site-defined client character set and Unicode.
A mapping file must minimally provide translation tables that map characters from the client character set to Unicode.
A mapping file may optionally provide translation tables that map characters from Unicode to the client character set. If the optional translation tables are not defined, the system derives them by inverting the corresponding mandatory tables.
If one of the following conditions exists, however, the optional translation tables become mandatory:
- More than one character from the client character set maps to a single Unicode character.
- More than one Unicode character maps to a single character of the client character set.