2 Database Systems versus File Systems(Cont) Drawbacks of using file systems(cont) Atomicity of updates Failures may leave database in an inconsistent state with partial updates carried out E.g. transfer of funds from one account to another should either complete or not happen at all Concurrent access by multiple users Concurrent accessed needed for performance Uncontrolled concurrent accesses can lead to inconsistencies E.g. two people reading a balance and updating it at the same time 标 Security problems Database System Concepts 1.6 @Silberschatz, Korth and SudarshanDatabase System Concepts 1.6 ©Silberschatz, Korth and Sudarshan 2 Database Systems versus File Systems(Cont.) Drawbacks of using file systems (cont.) Atomicity of updates Failures may leave database in an inconsistent state with partial updates carried out E.g. transfer of funds from one account to another should either complete or not happen at all Concurrent access by multiple users Concurrent accessed needed for performance Uncontrolled concurrent accesses can lead to inconsistencies – E.g. two people reading a balance and updating it at the same time Security problems