Commit Protocols Commit protocols are used to ensure atomicity across sites a transaction which executes at multiple sites must either be committed at all the sites,or aborted at all the sites. not acceptable to have a transaction committed at one site and aborted at another The two-phase commit(2PC)protocol is widely used The three-phase commit(3PC)protocol is more complicated and more expensive,but avoids some drawbacks of two-phase commit protocol.This protocol is not used in practice. Database System Concepts-6th Edition 19.20 @Silberschatz,Korth and SudarshanDatabase System Concepts - 6 19.20 ©Silberschatz, Korth and Sudarshan th Edition Commit Protocols Commit protocols are used to ensure atomicity across sites a transaction which executes at multiple sites must either be committed at all the sites, or aborted at all the sites. not acceptable to have a transaction committed at one site and aborted at another The two-phase commit (2PC) protocol is widely used The three-phase commit (3PC) protocol is more complicated and more expensive, but avoids some drawbacks of two-phase commit protocol. This protocol is not used in practice