Abstract: In a shared database system when several transactions are executed simultaneously, the consistency of database should be maintained. The techniques to ensure this consistency are concurrency control techniques. All concurrency-control schemes are based on the serializability property. The serializability properties requires that the data is accessed in a mutually exclusive manner; that means, while one transaction is accessing a data item no other transaction can modify that data item.

In this paper we had discussed various concurrency techniques, their advantages and disadvantages ­­and making comparison of optimistic, pessimistic and multiversion techniques. We have simulated the current environment and have analysis the performance of each of these methods.


Keywords: Concurrency, Locking, Serializability