If buffer retention effect is taken into account, validation schemes for optimistic concurrency control (OCC) should be approached in some different point of view: rather than killing the conflicting transactions immediately in the middle of their execution, it would be better to allow them to run to their completion for bringing the required data objects into main memory. In this respect, we propose a new validation scheme for OCC called reordering serial equivalence (RSE) by introducing reverse serializability, which ensures the correctness of RSE when we allow the serialization in the reverse order of transactions' commits.