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Overall Structure of a DBMS

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  Structure of a DBMS Disk Storage Data Dictionary The descriptive information is itself stored in a collection of special tables called the catalog tables. The catalog tables are also called the data dictionary. We can conclude that schema of a table is stored in data dictionary (as another table). DDL (Data Definition Language) commands deal with Data Dictionary. Data Data denotes actual data records that a user want to store. DML (Data Manipulation Language) commands deal with Data Files. Index Files To speedup data records extraction process as per requirements, Indices are created by the user. Indices are created on single column or on collection of columns having repeated values, Such Indices are also stored as database object in Index Files component.   Storage Control Unit Storage Control unit is responsible to manage disk storage as well as to control execution of commands. To accomplish these tasks different components are there as follows. ...
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Data Abstraction in DBMS

  Data Abstraction in DBMS Hiding Database Design complexities from users (which are not computer professionals) is nothing but known as Data Abstraction. ·         Data Abstraction feature provide easy way to retrieve data, from database. ·         There are three levels of abstraction.           Physical level Abstraction ·         Hiding the detail about “how the data is stored actually and where it is stored in database” from user is known as physical level abstraction. ·         The physical level describes complex low-level data structures in detail.           Logical level Abstraction ·         Hiding the detail about “what data are stored in the database, and what relationships exist among those data” from user is known...
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Advantages of DBMS

  Data Independence The DBMS provides an abstract view of the data that hides details such as, how data is stored, how it is represented. Abstraction of such kind provides a advantage of Data Independence.   Easy Access to Data DBMS provide many useful utility commands or techniques that are used to retrieve data as per user need in a efficient way.     Data Integrity Data Integrity can be defined as overall accuracy, completeness, and consistency of data.   DBMS provide a high level of Data Integrity by enforcing integrity constraints on data. ( We will discuss later Integrity Constraints ). Centralized Management In FPS, data scattered in various files, and files may be in different formats, writing new application programs to retrieve the appropriate data from different files is difficult. DBMS provides an easy way to join different relations ( tables ), so that we can extract required data from different relations in an easy manner.   Atomicity In many ...
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Database Concepts

  Data Data is the raw material that can be processed for any real life object for example Employee name, product name, student name student address etc.   Database Database can be defined as organized collection of related data. Database typically shows the relations and activities of organization entities. For example an organization college management may contain entities as student, Lecturer, classroom, laboratories and so on - which are related to each other , Database for a college management system will describe §   Activities related to Students, Lecturers, Laboratories and Classrooms . §   Relationship among the Students, Lecturers, Laboratories and Classrooms.   DBMS As we already defined Database is an organized repository or collection of related data but the question arise as an alone how Database can be managed by the user? So user needs a tool to manage the Database.   Database Management System or DBMS can...
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