Methods and apparatus, including computer program products, for communications in a distributed software system. An operation request from a remote computer is received, and provisionally executes an operation identified by the operation request. A first message is generated. The first message contains a transaction identifier identifying the operation request, an unsuccessful indicator flag, and a temporary data store. The temporary data store identifies tentatively written data generated by the operation. The first message is stored in a message store. If the successful completion of the operation is detected, a second message is generated. The second message contains the transaction identifier as well as a successful indicator flag. The second message is stored in the message store, and the message is transmitted to the remote computer. If the failure of the operation is detected, the message stored in the message store is transmitted to the remote computer.