Data Storage in DBMS
Data Storage and Querying in DBMS
At this point, it is worth while to note the difference between the terms file Organisation and the access method. A file organisation refers to the organisation of the data of a file into records, blocks, and access structures; this incbe and access structures: this includes the way records and blocks are placed on the storage medium and interlinked. An access method, on the other hand, is the way how the data can be retrieved based on the file Organisation.
Mostly the databases are stored. persistently on magnetic disks for the reasons given below:
- The databases being very large may not fit completely in the main memory.
- Storing the data permanently using the non-volatile storage and provide access to the users with the help of front end applications.
- Primary storage is considered to be very expensive and in order to cut short the cost of the storage per unit of data to substantially less.
Each hard drive is usually composed of a set of disk platters. Each disk platter has a layer of magnetic material deposited on its surface. The entire disk can contain a large amount of data, which is organised into smaller packages called BLOCKS (or pages). On most computers, one block is equivalent to 1 KB of data (= 1024 Bytes).