Phase 1:Obtaining a Decision Coordinator asks all participants to prepare to commit transaction T. C adds the records <prepare T>to the log and forces log to stable storage sends prepare T messages to all sites at which T executed Upon receiving message,transaction manager at site determines if it can commit the transaction if not,add a record <no T>to the log and send abort T message to C if the transaction can be committed,then: add the record <ready 7>to the log force all records for Tto stable storage send ready 7 message to C Transaction is now in ready state at the site Database System Concepts-7th Edition 23.8 ©Silberscha乜，Korth and SudarshanDatabase System Concepts - 7 23.8 ©Silberschatz, Korth and Sudarshan th Edition Phase 1: Obtaining a Decision ▪ Coordinator asks all participants to prepare to commit transaction Ti . • Ci adds the records <prepare T> to the log and forces log to stable storage • sends prepare T messages to all sites at which T executed ▪ Upon receiving message, transaction manager at site determines if it can commit the transaction • if not, add a record <no T> to the log and send abort T message to Ci • if the transaction can be committed, then: ▪ add the record <ready T> to the log ▪ force all records for T to stable storage ▪ send ready T message to Ci Transaction is now in ready state at the site