If you do not require customized function strings, you can use one of the system-provided function-string classes to provide default function strings. If you require class-scope or replication definition-scope customized strings, you must use the system-provided class—rs_sqlserver_function_class—in which you can customize function strings or create a derived or base function-string class.
If the connection for the database in which the function will be executed uses a system-provided function-string class or a derived class that inherits directly or indirectly from rs_default_function_class or a function-string class for a non-Sybase data server, default function strings are provided for every system function and user-defined function.
If the connection uses a user-created base function-string class (which does not inherit function strings) or a derived class that inherits from such a class, you must create function strings for every system function and user-defined function. Create them in the base class if you want them to be available in all its derived classes.