DATABASE ARCHITECTURE:-
The structure that brings all the components of a database together is known as the de Database architecture.
For example: Consider the case of the architecture of a school building. The archi cludes the various classrooms, offices, lihe he architccture INTRODUCTION 1 of the building is not just the visual style. It inclu corridors, gymnasiums, doors, windows. roof. and a large number of other such. these components are brought and placed together, the structure theat This is the low Various components of the database system together form the architecture of the database .
The architecture is further composed of the rules, procedures, and functions la and the items in the Chable your database to work and fulfill the business requirements. DBMS, we can define the architecture of a database under three different levels:
- The External level
- The Conceptual level
- The Internal level
The external level is at the highest level of database architecture. This is targeted for tha end users. In this view, only the restricted portion of the database is available to end users Decause an end user does not need to know everything about the structure of the entire database, rather than the amount of details he/she needs to work with. We may not want the end user to become confused with incredible amount of details by allowing him/her to have look at the entire database, or we may also not allow this for the purpose of security, where sensitive information must remain hidden from unwanted persons.
At this level, the database administrator (DBA) creates custom made mind tables, keeping in the specific kind of need for each user. These tables are also known as virtual tables or views, because they have no separate physical existence. Creating separate views of the database for the different users helps in ensuring the database different security, because when users have access only to the data that is needed and the access is chances of a limited, the security breakdown are minimized .
(ii) The Conceptual level:-
The conceptual level deals with the structure of the entire database. At this level, we are not interested with the raw data items anymore; we are interested with the structure of the database. This means we want to know the information about the attributes of each table, theST common attributes in different tables that help them to be combined, what kind of data can be t into these attributes, and so on. Conceptual or Logical schema is very useful for database. database administrators whose responsibility is to maintain the entire database. DBMS This database.
The level does not contain any storage level details i.e. it is independent of both software and hardware. The software independence means that the level is not dependent on the DBMS used to implement the database. The hardware independence means that the level specified does not depend on the hardware used in the database. Thus changes in either hardware of software will not affect the database design at the conceptual level.
(iii) The Internal level:-
This is the lowest level of database architecture. It deals with the deseription of how raw data items (like 1, ABC, D20 etc.) are stored in the physical storage devices (Hard Dise. CD DVD. Tape Drive etc.). It also describes the data type of these data items. the memory size of the items in the storage media, the location (physical address) of the items in the storage device and so on. This level is useful for database application developers and database es ponenms all of Nay, the ase. ata and ns tha administrator.
Sometimes, internal level is also referred as physical level. But there is a slight difference between them. Actually, physical level is one that is managed by the operating system under the direction of DBMS, while the internal level is managed by DBMS.
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