>> - commit every "n" inserts, where "n" is usually in the thousands.
>
> That exactly what I'm trying to do.

Unless you also have some triggers that repeatedly update the same rows,
you do not have to commit every "n" inserts, it will not speed up anything.

> transactions requires API calls, ...

No, they don't.

Ivan
http://www.volny.cz/iprenosil/interbase/