Implementation of Atomicity and Durability (Cont.) The shadow-database scheme: db-pointer db-pointer old copy of old copy of database new copy of database database (to be deleted) (a)Before update (b)After update Assumes disks do not fail Useful for text editors,but extremely inefficient for large databases(why?) Does not handle concurrent transactions Will study better schemes in Chapter 17. Database System Concepts-5th Edition,Sep 10,2005. 15.10 ©Silberschat乜，Korth and SudarshanDatabase System Concepts - 5 15.10 ©Silberschatz, Korth and Sudarshan th Edition, Sep 10, 2005. Implementation of Atomicity and Durability (Cont.) Assumes disks do not fail Useful for text editors, but extremely inefficient for large databases (why?) Does not handle concurrent transactions Will study better schemes in Chapter 17. The shadow-database scheme: