Hello!

> It is handy but it is against relation theory. Normalization! Why
> you can want to have two tables in a database with the same structure
> and the same data?..

To avoid limitation of 36gb per table? to be able to import/drop old data
that are stored in archive? it's not possible in real life to delete
100e6 records in one delete operation! but you can drop a table without
any impact on performance.
Regards.,
...michal