Begins a new transaction.
procedure StartTransaction; virtual;
Call the StartTransaction method to begin a new transaction against the database server. Before calling StartTransaction, an application should check the Active property. If TDATransaction.Active is True, indicating that a transaction is already in progress, a subsequent call to StartTransaction will raise EDatabaseError. An active transaction must be finished by call to Commit or Rollback before call to StartTransaction. Call to StartTransaction when connection is closed also will raise EDatabaseError.