An improved concurrency control method for R/W transaction

Two-phase locking protocol is widely used in flat transaction. But it's unsuitable for long duration transaction because of low efficiency to concurrent execution. There have existed lots of advanced transaction models to deal with long duration transaction. Yet few of them have been implemented in real systems so far. R/W transaction has the characteristic of long duration, which is frequently met in business process. This sort of transaction can be split into two parts, the former of which is reading part and the latter of which is writing part. Usually, there may be a period of time between reading and writing. A concurrency control method has been presented for R/W transaction, which could settle concurrency problems well when the relationship of the data sets is simple. However, the method will be hard to implement when the relationship becomes complex. So an improved method is presented now, which can settle the problems of R/W transaction much more generally.