Error Conditions with Persistent Messaging Code to handle messages has to take care of variety of failure situations (even assuming guaranteed message delivery) E.g.,if destination account does not exist,failure message must be sent back to source site When failure message is received from destination site,or destination site itself does not exist,money must be deposited back in source account Problem if source account has been closed get humans to take care of problem User code executing transaction processing using 2PC does not have to deal with such failures There are many situations where extra effort of error handling is worth the benefit of absence of blocking E.g.,pretty much all transactions across organizations Database System Concepts-7th Edition 23.19 ©Silberscha乜，Korth and SudarshanDatabase System Concepts - 7 23.19 ©Silberschatz, Korth and Sudarshan th Edition Error Conditions with Persistent Messaging ▪ Code to handle messages has to take care of variety of failure situations (even assuming guaranteed message delivery) • E.g., if destination account does not exist, failure message must be sent back to source site • When failure message is received from destination site, or destination site itself does not exist, money must be deposited back in source account ▪ Problem if source account has been closed • get humans to take care of problem ▪ User code executing transaction processing using 2PC does not have to deal with such failures ▪ There are many situations where extra effort of error handling is worth the benefit of absence of blocking • E.g., pretty much all transactions across organizations