An Example would be Order/Detail, my understanding is that you start a transaction and hold the lock until it gets the header and detail lines then commit it all at once (resource intensive) . In the relational model, the header and detail lines are each atomic transactions and are processed serially through optimistic locking. On updates the optimistic locking reads the row and update a timestamp and releases the lock. When it is time to update, sql reads the row and compares the timestamp. If the timestamps match commit else rollback to avoid the hidden update.
Is this a correct interpretation?