> I only have seen nightmares as a result of nested transactions. What are
> they good for?

We actually have them in interbase already if people only realized it.

Let's say you request a mass update or call a stored procedure which then
involves the actions of triggers. This operation gets part way complete
after performing many update operations but then it hits a brick wall and
has an exception. What happens to the updates already performed? They are
cancelled. Was a rollback necessary to cancel them? No, fortunately not.
What if InterBase didn't have this ability? That is what I would call a
nightmare.

So, yes, there is a huge need and benefit for a sub-transaction and
InterBase does support it. You just have to know how to use it and
appreciate it.

Regards,
Jason Wharton
CPS - Mesa AZ
http://www.ibobjects.com