The invention provides a mechanism for a transaction coordinator to indicate to a transaction participant that it supports a heuristic outcome, where a course of action has occurred which means that the transaction participant is unable to honor a transactional prior commitment to the transaction coordinator. The mechanism is such that a transaction participant that is incapable of communicating a heuristic outcome may ignore any such indication. A transaction participant may be incapable because it does not understand the concept of a heuristic outcome at all or because it does not have the ability to inform the transaction coordinator that a heuristic outcome has occurred.