Data Access Physical blocks are those blocks residing on the disk. Buffer blocks are the blocks residing temporarily in main memory. Block movements between disk and main memory are initiated through the following two operations: input(B)transfers the physical block B to main memory. output(B)transfers the buffer block B to the disk,and replaces the appropriate physical block there. Each transaction Ti has its private work-area in which local copies of all data items accessed and updated by it are kept. Ti's local copy of a data item X is called xi. We assume,for simplicity,that each data item fits in,and is stored inside,a single block. Database System Concepts,5th Edition,Oct 5,2006 17.8 @Silberschatz,Korth and SudarshanDatabase System Concepts, 5 17.8 ©Silberschatz, Korth and Sudarshan th Edition, Oct 5, 2006 Data Access Physical blocks are those blocks residing on the disk. Buffer blocks are the blocks residing temporarily in main memory. Block movements between disk and main memory are initiated through the following two operations: input(B) transfers the physical block B to main memory. output(B) transfers the buffer block B to the disk, and replaces the appropriate physical block there. Each transaction Ti has its private work-area in which local copies of all data items accessed and updated by it are kept. Ti 's local copy of a data item X is called xi . We assume, for simplicity, that each data item fits in, and is stored inside, a single block