1. Free Powerpoint Templates Page 1 Free Powerpoint Templates DBMS Unit -1 Overview of physical Storage Media

2. Free Powerpoint Templates Page 2 Cache  The cache is the fastest and most costly form of storage.  Cashe memory is relaively small.  Its use is managed by the computer hardware and software.  To pay attention to cache effects when designing query processing data structures and algorithms.

3. Free Powerpoint Templates Page 3 Main Memory  The storage medium used for data that are available to be operated on is mainmemory.  The genral purpose of main memory is to handle the machine instructions.  It is to small and to expensive.  Main memory are usually lost if a power failure or system crash occurs.

4. Free Powerpoint Templates Page 4 Flash Memory  Flash Memory differs from main memory in that stored data are retained even if power is turned off.  There are two types of flash memory,called Nand and Nor flash.  Nand has much capacity and cheap, it widely used for storage device.

5. Free Powerpoint Templates Page 5  Flash memory is widely used for storing the data in “USB” slot of computing devices.  It is also used for storing data.

6. Free Powerpoint Templates Page 6 Magnetic-disk storage The primary medium for the long-term online storage of data is the magnetic disk. The entire data stored in the magnetic disk. The system move the data from the disk to the main menory.

7. Free Powerpoint Templates Page 7 Optical Storage The most popular forms of optical storage are the Compact disk(CD) Which can hold the 700 mb of data and has a play time of about 80 minutes And the second is the Digital video disk This disk are write one and read many.

8. Free Powerpoint Templates Page 8 Tape storage Tap storage is used primarily for backup and archival data It is cheaper than disks, access to data is much slower, because the tap must be accessed sequentially from the beginning. Tap storage is referred as sequential – access storage. Tapes have a high capacity (40 to 300 gigabyte)

9. Free Powerpoint Templates Page 9 Types of file organization A file is organized logically as a basic construct in operating system, so we shall assume the existence of an underlying file system. Each file are stored in the fixed-length storage units called blocks. Generally the size of the block is 4 to 8 kb default, but many database allow the block size to be specified at when the instance is create.

10. Free Powerpoint Templates Page 10 Fixed length records Assume that we give the fixed length of the particular field But there is one problem if the data is more than the length then it would require the 2 block access to read or write such a record. In this structured it is difficult do delete record from this structure.

11. Free Powerpoint Templates Page 11 Variable length records Fixed length attributes,such as numeric value,dates or fixed value Variable length attribute such as Varchar Types, are represented in the initial part of record by a pair (offset, length).

12. Free Powerpoint Templates Page 12 Organization of Records in Files Heap File Organization Sequential file organization Hashing file Organization

13. Free Powerpoint Templates Page 13 Heap File Organization Any record can be placed anywhere in the file where there is space for the record. There is no ordering of records. Typically, there is a single file for each relation.