Chapter Summary
n The Database Management System (DBMS) is now the underlying framework of the information system
and has fundamentally changed the way that many organizations operate. The database system remains a very
active research area and many significant problems have still to be satisfactorily resolved.
n The predecessor to the DBMS was the file-based system, which is a collection of application programs that
perform services for the end-users, usually the production of reports. Each program defines and manages its
own data. Although the file-based system was a great improvement on the manual filing system, it still has
significant problems, mainly the amount of data redundancy present and program–data dependence.
n The database approach emerged to resolve the problems with the file-based approach. A database is a shared
collection of logically related data, and a description of this data, designed to meet the information needs of
an organization. A DBMS is a software system that enables users to define, create, maintain, and control
access to the database. An application program is a computer program that interacts with the database by
issuing an appropriate request (typically an SQL statement) to the DBMS. The more inclusive term database
system is used to define a collection of application programs that interact with the database along with the
DBMS and database itself.
n All access to the database is through the DBMS. The DBMS provides a Data Definition Language (DDL),
which allows users to define the database, and a Data Manipulation Language (DML), which allows users
to insert, update, delete, and retrieve data from the database.
n The DBMS provides controlled access to the database. It provides security, integrity, concurrency and
recovery control, and a user-accessible catalog. It also provides a view mechanism to simplify the data that
users have to deal with.
n The DBMS environment consists of hardware (the computer), software (the DBMS, operating system, and
applications programs), data, procedures, and people. The people include data and database administrators,
database designers, application developers, and end-users.
n The roots of the DBMS lie in file-based systems. The hierarchical and CODASYL systems represent the
first-generation of DBMSs. The hierarchical model is typified by IMS (Information Management System)
and the network or CODASYL model by IDS (Integrated Data Store), both developed in the mid-1960s.
The relational model, proposed by E. F. Codd in 1970, represents the second-generation of DBMSs. It has
had a fundamental effect on the DBMS community and there are now over one hundred relational DBMSs.
The third-generation of DBMSs are represented by the Object-Relational DBMS and the Object-Oriented
DBMS.
n Some advantages of the database approach include control of data redundancy, data consistency, sharing of
data, and improved security and integrity. Some disadvantages include complexity, cost, reduced performance,
and higher impact of a failure.
n The Database Management System (DBMS) is now the underlying framework of the information system
and has fundamentally changed the way that many organizations operate. The database system remains a very
active research area and many significant problems have still to be satisfactorily resolved.
n The predecessor to the DBMS was the file-based system, which is a collection of application programs that
perform services for the end-users, usually the production of reports. Each program defines and manages its
own data. Although the file-based system was a great improvement on the manual filing system, it still has
significant problems, mainly the amount of data redundancy present and program–data dependence.
n The database approach emerged to resolve the problems with the file-based approach. A database is a shared
collection of logically related data, and a description of this data, designed to meet the information needs of
an organization. A DBMS is a software system that enables users to define, create, maintain, and control
access to the database. An application program is a computer program that interacts with the database by
issuing an appropriate request (typically an SQL statement) to the DBMS. The more inclusive term database
system is used to define a collection of application programs that interact with the database along with the
DBMS and database itself.
n All access to the database is through the DBMS. The DBMS provides a Data Definition Language (DDL),
which allows users to define the database, and a Data Manipulation Language (DML), which allows users
to insert, update, delete, and retrieve data from the database.
n The DBMS provides controlled access to the database. It provides security, integrity, concurrency and
recovery control, and a user-accessible catalog. It also provides a view mechanism to simplify the data that
users have to deal with.
n The DBMS environment consists of hardware (the computer), software (the DBMS, operating system, and
applications programs), data, procedures, and people. The people include data and database administrators,
database designers, application developers, and end-users.
n The roots of the DBMS lie in file-based systems. The hierarchical and CODASYL systems represent the
first-generation of DBMSs. The hierarchical model is typified by IMS (Information Management System)
and the network or CODASYL model by IDS (Integrated Data Store), both developed in the mid-1960s.
The relational model, proposed by E. F. Codd in 1970, represents the second-generation of DBMSs. It has
had a fundamental effect on the DBMS community and there are now over one hundred relational DBMSs.
The third-generation of DBMSs are represented by the Object-Relational DBMS and the Object-Oriented
DBMS.
n Some advantages of the database approach include control of data redundancy, data consistency, sharing of
data, and improved security and integrity. Some disadvantages include complexity, cost, reduced performance,
and higher impact of a failure.
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