A novel optimistic concurrency control (OCC) protocol for distributed high-performance transaction systems is presented. Unlike other proposals for OCC in distributed systems, this scheme limits the number of restarts by acquiring locks to guarantee a failed transaction a successful second execution. Lock acquisition and validation are imbedded in the commit protocol in order to avoid any extra messages. Deadlocks are avoided by requesting all locks at once before performing validation. The protocol is fully distributed and employs parallel validation and lock acquisition. A main advantage compared with distributed locking schemes is that locks are held only during commit processing in general, thus considerably reducing the degree of lock contention. As first simulation results have confirmed, this is of particular benefit for high-performance transaction-processing complexes with fast processors.