You can define a logical name for a character set name. Doing
    so allows easy portability of applications across national
    boundaries. You can use this logical name or parameter anywhere
    you use a character set name in SQL. SQL translates the logical
    name or parameter at compile time for precompiled SQL and SQL
    module language, or at run time for dynamic SQL and interactive
    SQL.

    The logical name can begin with any of the following:

    o  RDBVMS$

    o  RDB$

    o  SQL$

       Oracle Rdb recommends that you begin logical names with RDB$.