Data Schema & Data instances

Data Schema

A schema is the design of a database. It defines however the info is organized and how the relations among them are associated. The overall description of the information or data is named the information schema.

 It can be categorized into three parts shown in figure

• Physical Schema
• Logical Schema
• View Schema

A physical schema can be defined as the design of an information (database) at its physical level. In this level, it is expressed how data is stored in blocks of storage.

A logical schema can be defined as the design of an information (database) at its logical level. In this level, the programmers as well as the database administrator (DBA) work. At this level, data can be described as certain types of data records which can be stored in the form of data structures. However, the internal details will be remaining hidden at this level.

A View schema can be defined as the design of the database at view level which generally describes end-user interaction with database systems.

Data instances

The atmosphere of information or database is alleged to be instance. A database instance or an ‘instance’ is created from the background processes required by the database.

These methods typically embrace a process monitor, session monitor, lock monitor, etc.