Database Systems: Lecture 10 - Overview of Database Design Process includes Data Storage (Disk Storage Devices, Files of Records, Operations on Files, Unordered Files, Ordered Files, Hashed Files, RAID Technology), Indexing Structures for Files. | Overview of Database Design Process Data Storage, Indexing Structures for Files Outline Data Storage Disk Storage Devices Files of Records Operations on Files Unordered Files Ordered Files Hashed Files RAID Technology Indexing Structures for Files Types of Single-level Ordered Indexes Multilevel Indexes Dynamic Multilevel Indexes Using B-Trees and B+-Trees Indexes on Multiple Keys Disk Storage Devices Preferred secondary storage device for high storage capacity and low cost. Data stored as magnetized areas on magnetic disk surfaces. A disk pack contains several magnetic disks connected to a rotating spindle. Disks are divided into concentric circular tracks on each disk surface. Track capacities vary typically from 4 to 50 Kbytes or more Disk Storage Devices (contd.) A track is divided into smaller blocks or sectors because it usually contains a large amount of information A track is divided into blocks. The block size B is fixed for each system. Typical block | Overview of Database Design Process Data Storage, Indexing Structures for Files Outline Data Storage Disk Storage Devices Files of Records Operations on Files Unordered Files Ordered Files Hashed Files RAID Technology Indexing Structures for Files Types of Single-level Ordered Indexes Multilevel Indexes Dynamic Multilevel Indexes Using B-Trees and B+-Trees Indexes on Multiple Keys Disk Storage Devices Preferred secondary storage device for high storage capacity and low cost. Data stored as magnetized areas on magnetic disk surfaces. A disk pack contains several magnetic disks connected to a rotating spindle. Disks are divided into concentric circular tracks on each disk surface. Track capacities vary typically from 4 to 50 Kbytes or more Disk Storage Devices (contd.) A track is divided into smaller blocks or sectors because it usually contains a large amount of information A track is divided into blocks. The block size B is fixed for each system. Typical block sizes range from B=512 bytes to B=4096 bytes. Whole blocks are transferred between disk and main memory for processing. Disk Storage Devices (contd.) Disk Storage Devices (contd.) A read-write head moves to the track that contains the block to be transferred. Disk rotation moves the block under the read-write head for reading or writing. A physical disk block (hardware) address consists of: a cylinder number (imaginary collection of tracks of same radius from all recorded surfaces) the track number or surface number (within the cylinder) and block number (within track). Reading or writing a disk block is time consuming because of the seek time s and rotational delay (latency) rd. Double buffering can be used to speed up the transfer of contiguous disk blocks. Disk Storage Devices (contd.) Records Fixed and variable length records Records contain fields which have values of a particular type ., amount, date, time, age Fields themselves may be fixed .
