Isildo,

>It's possible to start more than one explicit transaction?

Yes, as many as you want I believe, but each TIBOQuery or TIBOTable
component should only have one transaction (one transaction can span
several connections though). You can have separate queries/tables for each
form you're using if you want to.

>What should I use? Implicited or explicited transactions?

It's up to you. Maybe explicit transactions with AutoCommit set to true
will suit your needs? Whatever you do, I don't think you ought to start
your transaction explicitly - IBO will do it for you whenever necessary
(well, maybe not whenever necessary, but I think neither of us two are
experts enough to experience such circumstances). You may have to change
your check for InTransaction to TransactionIsActive though - don't remember
why I prefer TransactionIsActive, but I think it was a Jason recommendation.

>What's the use for explicites transaction component?

It's useful whenever you want to make sure that a bunch of changes are
either done completely or not at all. For instance if you work with banking
systems - you don't want to loose or double any money in transfer.

HTH,
Set