Introduction to Database Management Systems
A Database Management System (DBMS) is the software system that allows users to define, create and maintain a
database and provides controlled access to the data. A database is a logically coherent collection of data with some
inherent meaning. The term database is often used to refer to the data itself. A complete DBMS usually consists of hardware, software including utilities, data, users and procedures.
The hardware is the actual computer system used for keeping and accessing the database. In large organizations, the
hardware for such a system typically consists of a network with a central server and many client programs running on
desktops. The server is the central processor where the database is physically located. The server usually has a more
powerful processor because it handles the data retrieval operations and most of the actual data manipulation. The clients
are the programs that interact with the RDBM and run on the personal desktops at the user's end to access the database.
A DBMS and its clients can also reside in a single computer. In that case there is usually only one user at a time
accessing the database, either a single user or a single personal database management system accessed by several users
at different times. The actual configuration of the network varies from organization to organization.
The software is the actual DBMS. In a client/server network, the DBMS allows for data handling programs residing on
the server and client programs on each desktop. In a single-user system usually only one piece of software handles
everything. The DBMS allows the users to communicate with the database. In a sense, it is the mediator between the
database and the users. Each client station or each individual user can be given different levels of access to the data.
Some will be allowed to change portions of the database structure, some can change the existing data, and others will
only be allowed to view the data. The DBMS controls access and helps maintain the consistency of the data.
Utilities are usually included as part of the DBMS. Some of the most common utilities are report writers, application development
tools and other design aids. Examples of DBMS software include Microsoft AccessTM, Oracle Corporation Personal OracleTM, and IBM DB2TM.The database should contain all the data needed by the organization. One of the major features of databases is that the
actual data are separated from the programs that use the data. The set of facts represented in a database is called the Universe of Discourse (UOD). The UOD should only include facts that form a logically coherent collection and that are relevant to its users. For this reason, a database should always be designed, built and populated for a particular audience
and for a specific purpose. Emphasis is on the relevant data pertaining to one or more objects, or entities.The characteristics that describe or qualify an entity are called attributes of the entity. For instance, in a student database, the basic entity is the student. Information recorded about that entity might be first and last name, major, grade point average, home address, current address, date of birth, and class level. These are the attributes of the student entity. The
system would not be interested in the type of clothes, the number of friends, the movies the student attends, and so on. That is, this information is not relevant to the user and should not be part of the UOD.
database and provides controlled access to the data. A database is a logically coherent collection of data with some
inherent meaning. The term database is often used to refer to the data itself. A complete DBMS usually consists of hardware, software including utilities, data, users and procedures.
The hardware is the actual computer system used for keeping and accessing the database. In large organizations, the
hardware for such a system typically consists of a network with a central server and many client programs running on
desktops. The server is the central processor where the database is physically located. The server usually has a more
powerful processor because it handles the data retrieval operations and most of the actual data manipulation. The clients
are the programs that interact with the RDBM and run on the personal desktops at the user's end to access the database.
A DBMS and its clients can also reside in a single computer. In that case there is usually only one user at a time
accessing the database, either a single user or a single personal database management system accessed by several users
at different times. The actual configuration of the network varies from organization to organization.
The software is the actual DBMS. In a client/server network, the DBMS allows for data handling programs residing on
the server and client programs on each desktop. In a single-user system usually only one piece of software handles
everything. The DBMS allows the users to communicate with the database. In a sense, it is the mediator between the
database and the users. Each client station or each individual user can be given different levels of access to the data.
Some will be allowed to change portions of the database structure, some can change the existing data, and others will
only be allowed to view the data. The DBMS controls access and helps maintain the consistency of the data.
Utilities are usually included as part of the DBMS. Some of the most common utilities are report writers, application development
tools and other design aids. Examples of DBMS software include Microsoft AccessTM, Oracle Corporation Personal OracleTM, and IBM DB2TM.The database should contain all the data needed by the organization. One of the major features of databases is that the
actual data are separated from the programs that use the data. The set of facts represented in a database is called the Universe of Discourse (UOD). The UOD should only include facts that form a logically coherent collection and that are relevant to its users. For this reason, a database should always be designed, built and populated for a particular audience
and for a specific purpose. Emphasis is on the relevant data pertaining to one or more objects, or entities.The characteristics that describe or qualify an entity are called attributes of the entity. For instance, in a student database, the basic entity is the student. Information recorded about that entity might be first and last name, major, grade point average, home address, current address, date of birth, and class level. These are the attributes of the student entity. The
system would not be interested in the type of clothes, the number of friends, the movies the student attends, and so on. That is, this information is not relevant to the user and should not be part of the UOD.
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