Can anyone help me ?

I have moved recently to Interbase 6 (I used to use Paradox) and I
don't know how I have to work on it for best performance and less
problems.
I'm using a IBDatabase (Dialect 3) and a IBTransaction with the
following parameters:
- read_committed
- rec_version
- nowait
So I connected all my IBQuery to the IBDatabase. Then I noticed that
this component does not support RequestLive. So I attached a
IBUpdateSQL to each IBQuery. In that way the users change the data.
Is it the best way to let the users update their data ?

There is something wrong with that configuration because I get this
error when more than two users try to access/update the same record...

"lock conflict on no wait transaction attempt to store duplicate
(visible to active transactions) in unique index "INDEX_NAME" "

Is this error caused by IBTransaction configuration ? Which are the
best parameters ? Do I have to use STARTTRANSACTION, ROLLBACK,
COMMIT ? When ? Where ?

Thank you very much in advance,
Paulo Albuquerque