using 1 ctl file there exists four combinations.
- insert data from multiple data files to a single table
- insert data from a single data file to multiple tables
- insert data from single data file to single table
- insert data from multiple files to multiple tables.
the first three are possible for any situation. but the fourth case is possible only when the structure of all tables is the same. otherwise we have to go for multiple ctl files.
more info can be found here