In addition to Ivans answer...

> > I'd like to know if Firebird supports 2 levels of transactions.
> >
> > To be clear:
> > I would like to open a main transaction I will be able at any time to

commit or rollback. That exists for sure. But I

> also would like inside that transaction, to open other ones I could commit

or rollback as well.

> > The objective is to implement a single undo function which was not

planned before. Another possibility I have been

> told, but I don't know for Firebird, it to set a serie of milestones you

can at anytime in the main transaction rollback

> to one of these.
> >

You cannot start transaction inside another transaction. So your
mega-undo-fuction
cannot be done.

With regards,

Martijn Tonies
Database Workbench - developer tool for InterBase, Firebird, MySQL & MS SQL
Server.
Upscene Productions
http://www.upscene.com