ACID Properties A transaction is a unit of program execution that accesses and possibly updates various data items.To preserve the integrity of data the database system must ensure: Atomicity.Either all operations of the transaction are properly reflected in the database or none are. Consistency.Execution of a transaction in isolation preserves the consistency of the database. Isolation.Although multiple transactions may execute concurrently, each transaction must be unaware of other concurrently executing transactions.Intermediate transaction results must be hidden from other concurrently executed transactions. That is,for every pair of transactions Ti and Ti,it appears to Ti that either Ti,finished execution before T;started,or T;started execution after 7;finished. Durability.After a transaction completes successfully,the changes it has made to the database persist,even if there are system failures. Database System Concepts-5th Edition,Sep 10,2005. 15.4 ©Silberschat乜，Korth and SudarshanDatabase System Concepts - 5 15.4 ©Silberschatz, Korth and Sudarshan th Edition, Sep 10, 2005. ACID Properties Atomicity. Either all operations of the transaction are properly reflected in the database or none are. Consistency. Execution of a transaction in isolation preserves the consistency of the database. Isolation. Although multiple transactions may execute concurrently, each transaction must be unaware of other concurrently executing transactions. Intermediate transaction results must be hidden from other concurrently executed transactions. That is, for every pair of transactions Ti and Tj , it appears to Ti that either Tj , finished execution before Ti started, or Tj started execution after Ti finished. Durability. After a transaction completes successfully, the changes it has made to the database persist, even if there are system failures. A transaction is a unit of program execution that accesses and possibly updates various data items.To preserve the integrity of data the database system must ensure: