An Empirical Study on Extension of Three Phase Commit Protocol for Concurrency Control in Distributed System

Abstract

In distributed system two phase commit protocol and three phase commit protocol are used for concurrency control. But both protocol has disadvantage of blocking and global abortion (of transaction) respectivily. In my research paper, I have designed an algorithm for successfully submition of transaction even if any site (primary or secondary site) has voted to abort. For this I have used a table TIT (Transaction Information Table) which has three fields namely-1) Transaction Id 2) Site Id 3) Value and three messages for communication purpose between sites. I have also used a local clock which run at regular interval for checking the value of database object (describe in detail in further part of paper). For any transaction if any site votes to abort so it’s save TIT’s value=”Inconsistent” with respect to that site and transaction on other sites commit suceessfully. So there is inconsistency that has arisen. To remove this inconsistency I have introduced the concept of local clock which runs at each site. This clock runs at regular intervals and checks for the database objects for which the TIT’s value= “Inconsistent”. Then it issues a transaction to remove this inconsistency. Recovery transaction will be originated by coordinator through message passing. After receiving the message inconsistent site will update its database by fetching the transaction related information from either their nearest site or the coordinator.

Keywords: Concurrency Control, Two-Phase Commit Protocol, Three Phase Commit Protocol, Primary Sites, Secondary Sites

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