The more I read about transaction, the more I learn about my ignorance!
There should really be a "deep inside" tech sheet with tons of real
world situation as samples, since I'm not the only one confused, I guess.
btw, I've also got the feeling that without PessimisticLock (that I
always use) a lot of data risks to be overwritten in many apps around
while updating.
dbExpress updates sending the whole old value fields to locate the
record, so if something is changed the update fails.
IBO relies upon transactions, but it's not very clear how correctly
manage things, and if/when PessimisticLock is always needed to avoid
data being overwriten by someone updating the same record in a
different time, sending the value in it's (old) buffer.
But I have to take the time to read previous messages and formulate
more precise questions, I guess...

thanks
Marco Menardi