Not all transactions care about repeatable reads. They are willing to forego problems arising with phantoms. We’ll call this level “nonrepeatable reads”. (This is called degree 2 isolation also called cursor stability (CS)). CS differs from RR in that read locks are discarded once a tuple has been read. Write locks on tuples, like RR, are held to the end of the transaction. Note that CS executions are not truely serializable (because of the nonrepeatability of reads).