Distributed Timestamp-Based Protocols Timestamp based concurrency-control protocols can be used in distributed systems Each transaction must be given a unique timestamp Main problem:how to generate a timestamp in a distributed fashion Each site generates a unique local timestamp using either a logical counter or the local clock. Global unique timestamp is obtained by concatenating the unique local timestamp with the unique identifier. local unique site timestamp identifier global unique identifier Database System Concepts-7th Edition 23.34 @Silberschatz,Korth and SudarshanDatabase System Concepts - 7 23.34 ©Silberschatz, Korth and Sudarshan th Edition Distributed Timestamp-Based Protocols ▪ Timestamp based concurrency-control protocols can be used in distributed systems ▪ Each transaction must be given a unique timestamp ▪ Main problem: how to generate a timestamp in a distributed fashion • Each site generates a unique local timestamp using either a logical counter or the local clock. • Global unique timestamp is obtained by concatenating the unique local timestamp with the unique identifier