On the v2.1 Release Notes:
Registering a Character Set in a Database
To register the module in a database, you have two options:
• Use the CREATE COLLATION statement, OR—
• Run the procedure sp_register_character_set, the source for which can be found in misc/intl.
sql beneath your Firebird 2.1 root
There is only one option. It's the sp_register_character_set way.