To validate a transaction prior to commit, the follow- ing steps are executed. All replicas other than the pri- mary have to execute the transaction operations and ver- ify that the returned results match the results previously obtained in the coordinator. Given that the transaction executes in the same snapshot in every replica (as ex- plained in the BEGIN operation), if the coordinator was correct, all other correct replicas should obtain the same results. If the coordinatorwas faulty, the results obtained by the replicas will not match those sent by the client. In this case, correct replicas will abort the transaction and the client throws an exception signaling Byzantine be- havior. In.
