By default, transactional processing of messages is not enabled. This means that the MQ server will commit the changes as soon as a message is sent or retrieved. If sending or receiving more than one message on a given session, the Session Type can be set to transacted. In transacted mode, the MQ server will only commit the changes if the Commit attribute is set to true on the Close Session or Commit/Rollback Session tasks. For example, if the MQ Send Message Task was in a loop and an error occurred trying to send the second message, the first message would be ignored by the MQ server.