When executing unknown SQL statement one should be ready that this is START TRANSACTION or COMMIT, therefore value returned by I***::execute() function should be assigned to current transaction (that's exactly what ISQL in Alpha2 does). But in case of any error API returns NULL (causing transaction leek in ISQL). To avoid need to analyze IStatus before assigning to current transaction in any user program it's good idea to make API return on error old transaction interface pointer.