webHonest4u

  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. ...

  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...