Purpose of Database Systems (Cont.) Drawbacks of using file systems(cont.) Atomicity of updates Failures may leave database in an inconsistent state with partial updates carried out Example: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 Example:Two people reading a balance and updating it at the same time Security problems Hard to provide user access to some,but not all,data Database systems offer solutions to all the above problems Database System Concepts-5th Edition,May 23,2005 1.5 @Silberschatz,Korth and SudarshanDatabase System Concepts - 5 1.5 ©Silberschatz, Korth and Sudarshan th Edition, May 23, 2005 Purpose of Database Systems (Cont.) Drawbacks of using file systems (cont.) Atomicity of updates  Failures may leave database in an inconsistent state with partial updates carried out  Example: 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 – Example: Two people reading a balance and updating it at the same time Security problems  Hard to provide user access to some, but not all, data Database systems offer solutions to all the above problems