This chapter provides an overview of transaction processing. It first motivates the problems of atomicity, consistency, isolation and durability, and introduces the notion of ACID transactions. It then presents some naive schemes, and their drawbacks, thereby motivating the techniques described in Chapters 16 and 17. The rest of the chapter describes the notion of schedules and the concept of serializability. | Chapter 15: Transactions Database System Concepts, 5th Ed. ©Silberschatz, Korth and Sudarshan See for conditions on reuse Chapter 15: Transactions s Transaction Concept s Transaction State s Concurrent Executions s Serializability s Recoverability s Implementation of Isolation s Transaction Definition in SQL s Testing for Serializability. Database System Concepts 5th Edition, Sep 12, 2006. 15. ©Silberschatz, Korth and Sudarshan Transaction Concept s A transaction is a unit of program execution that accesses and possibly updates various data items. s . transaction to transfer $50 from account A to account B: 1. read(A) 2. A := A – 50 3. write(A) 4. read(B) 5. B := B + 50 6. write(B) s Two main issues to deal with: q q Failures of various kinds, such as hardware failures and system crashes Concurrent execution of multiple transactions Database System Concepts 5th Edition, Sep 12, 2006. 15. ©Silberschatz, Korth and Sudarshan Example of Fund Transfer s Transaction to transfer $50 from account A to account B: 1. read(A) 2. A := A – 50 3. write(A) 4. read(B) 5. B := B + 50 6. .
