1  –  CASCADE

    Specifies that you want SQL to modify any storage map that uses
    this index to be a NO PLACEMENT VIA INDEX storage map.

2  –  IF_EXISTS

    Prevents SQL command language from displaying error messages if
    the referenced object does not exist in the database.

3  –  index-name

    Specifies the name of the index definition you want to delete.

4  –  RESTRICT

    Prevents the removal of an index if it is referenced by any other
    object within an Oracle Rdb database. RESTRICT is the default.