What Do You Know About The Three-level Architecture Of Database System? Can You Describe Internal View Level?


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Muhammad Azhar Profile
Muhammad Azhar answered
The three-level architecture is also known as three-schema architecture. The purpose of the three-level architecture is to separate the user applications and the physical database. The reasons of this separation are:
(I)        Different users need different views of the same data.
(ii)      Users should not have to deal directly with the physical database storage details.
(iii)      The DBA should be able to change the database storage structure or storage device without affecting other user's views etc.
The three-level architecture is divided into three view levels;
External view level, Conceptual view level and Internal view level.

Internal View Level:
The internal view level is also referred to as physical view level. It describes the physical storage structures of database and file organizations used to store data on physical storage devices. The internal level describes how the data is stored in the database. It works with operating system and DBMS for storing and retrieving data to and from the storage devices. An internal record is a single stored record. It is a storage unit that is passed up to the internal level. The operating system is responsible for storing and retrieving internal records. It means that operating system creates the physical record interface.

The internal view level is described by means of the internal schema, which defines the various record types, storage space allocation for data and indexes etc. The internal schema is written in DDL.
thanked the writer.
divya kaura
divya kaura commented
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Anonymous Profile
Anonymous answered
Three schema architecture is used to separate the physical database and user applications. Three schema architecture is a convenient tool with which users can visualize the schema levels in a database system. Many Database management systems support the three level architecture to some extent but they do not separate the three levels of schema completely. Some DBMSs use conceptual schema to support physical level details.

Some DBMSs use external schemas to support user views. If you pay attention to three schemas then you come to the point that there schemas are only descriptions of data and actual data exists at physical level. A DBMS that clearly separates the three levels must have mappings between schemas to transform requests from one level of schema to another level. As its name specifies that it has three levels of schemas.
(1) Internal Level
(2) Conceptual Level
(3) External Level
Each level has its own schema. I will only discuss internal level as you have asked only about this.

Internal Level: Internal level has internal schema which uses physical data model. Internal schema describes the physical storage structure of the database. Physical data model describes as how data is stored in computer by representing information such as record formats and record ordering. Physical data model also provides access path.

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