No DML or DDL possible in functions called by function-based indexes.
Functions called in function-based indexes cannot be used to perform any DML or DDL so although the function called by a function-based index on DUAL runs under SYS, it is very restricted in what it is allowed to do. The article suggests that you can use this method to run any old function under the SYS user. You can't.
Biting the hand that feeds IT
