Concurrency Control

Part II Concurrency Control

Concurrency Control

AU: May-19, Marks 15

• One of the fundamental properties of a transaction is isolation.

• When several transactions execute concurrently in the database, however, the isolation property may no longer be preserved.

• A database can have multiple transactions running at the same time. This is called concurrency.

• To preserve the isolation property, the system must control the interaction among the concurrent transactions; this control is achieved through one of a variety of mechanisms called concurrency control schemes.

• Definition of concurrency control: A mechanism which ensures that simultaneous execution of more than one transactions does not lead to any database inconsistencies is called concurrency control mechanism.

• The concurrency control can be achieved with the help of various protocols such as - lock based protocol, Deadlock handling, Multiple Granularity, Timestamp based protocol, and validation based protocols.

Review Question                                                

1. What is concurrency control? How it is implemented in DBMS? Briefly elaborate diagrams and examples. AU: May-19, Mark 15