DBMS – Instances and Schemas

Tutorials Point 

Topics: DBMS, Schemas, Software

Transcript Summary

DBMS, instances and schemas are discussed. Database Management System (DBMS) is software designed to store, retrieve, define, and manage data in a database. The presenter discusses the difference between instances, schemas, and physical data independence. 

The presenter discusses the difference between instances and schemas. There are insert, delete, and update operations available as a result of the database content that will be changing frequently and regularly. This will represent the content of the DBMS because it will depend upon the variation of the time. An instance of a database means at any instant of time, the content of the database will be known as the instance of the DBMS. The database content is regularly updating and changing some insertion and deletion operations. The data type of the name will be string, text, or varchar. In this case, the logical description of a database is known as the schema of the data. The content of the database as an instance should be considered when making database designs, insertion and deletion operations, and physical data independence. The content of the database should also consider the different data types that are there such as string, text, or varchar. 

A schema is the logical description of a database. The software in which the database is going to get implemented shouldn’t be bothered. The schema can be of two types: a physical schema and a logical schema. The disk physical schema describes the database design at a physical level. The data will then be stored on the database. This is known as the physical level. The physical level  describes the database design known as the physical schema. In the case of the physical level, the topic of how data will be stored in the database is discussed. A logical schema describes the database design at the logical level. In the case of the logical level, data that is stored on to the database and the interrelationship between data is discussed. The program that can be used as a schema does not need to be bothered with any kind of syntax, grammar, kind of keywords, or punctuation symbols. A programmer can program in plain English and that is known as the respective algorithm of the program. 

A physical data independence means that the application programs are not dependent on the physical schema and do not carry out any changes. The physical data independence application program does not need to require any changes and therefore does not need to be rewritten if the physical schema changes. If the database has migrated from one physical schema to another physical schema, the respective application program which is written on the database will be used by different users, name users, application programmers or other users. Instances, schemas, and physical data independence can all help programmers better understand what to write and any type of database designs. They can also help programmers know what content the database needs and the data types that are necessary to make the database designs work for the users and the other users that are using it. 

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