Database Management System:
- A database-management system (DBMS) is a collection of interrelated data and a set of
programs to access those data.
- The DBMS is a general purpose software system that facilitates the process of defining
constructing and manipulating databases for various applications.
Goals of DBMS:
The primary goal of a DBMS is to provide a way to store and retrieve database
information that is both convenient and efficient
1.Manage large bodies of information
2. Provide convenient and efficient ways to store and access information
3. Secure information against system failure or tampering
4. Permit data to be shared among multiple users
Properties of DBMS:
- 1.A Database represents some aspect of the real world. Changes to the real world reflected in
the database.
- 2.A Database is a logically coherent collection of data with some inherent meaning.
- 3.A Database is designed and populated with data for a specific purpose.
Need of DBMS:
- 1. Before the advent of DBMS, organizations typically stored information using a “File
Processing Systems”.
Example of such systems is File Handling in High Level Languages like C, Basic and COBOL
etc., these systems have Major disadvantages to perform the Data Manipulation. So to
overcome those drawbacks now we are using the DBMS.
- 2.Database systems are designed to manage large bodies of information.
- 3. In addition to that the database system must ensure the safety of the information stored,
despite system crashes or attempts at unauthorized access. If data are to be shared among
several users, the system must avoid possible anomalous results.
ADVANTAGES OF A DBMS OVER FILE SYSTEM:
Using a DBMS to manage data has many advantages:
Data Independence:
Application programs should be as independent as possible from details of data
representation and storage. The DBMS can provide an abstract view of the data to insulate
application code from such details.
Efficient Data Access:
A DBMS utilizes a variety of sophisticated techniques to store and retrieve data
efficiently. This feature is especially important if the data is stored on external storage devices.
Data Integrity and Security:
If data is always accessed through the DBMS, the DBMS can enforce integrity
constraints on the data. For example, before inserting salary information for an employee, the
DBMS can check that the department budget is not exceeded. Also, the DBMS can enforce
access controls that govern what data is visible to different classes of users
Concurrent Access and Crash Recovery:
A database system allows several users to access the database concurrently. Answering
different questions from different users with the same (base) data is a central aspect of an
information system. Such concurrent use of data increases the economy of a system.
An example for concurrent use is the travel database of a bigger travel agency. The
employees of different branches can access the database concurrently and book journeys for
their clients. Each travel agent sees on his interface if there are still seats available for a specific
journey or if it is already fully booked.
A DBMS also protects data from failures such as power failures and crashes etc. by the
recovery schemes such as backup mechanisms and log files etc.
Data Administration:
When several users share the data, centralizing the administration of data can offer
significant improvements. Experienced professionals, who understand the nature of the data
being managed, and how different groups of users use it, can be responsible for organizing the
data representation to minimize redundancy and fine-tuning the storage of the data to make
retrieval efficient.
Reduced Application Development Time:
DBMS supports many important functions that are common to many applications
accessing data stored in the DBMS. This, in conjunction with the high-level interface to the
data, facilitates quick development of applications. Such applications are also likely to be more
robust than applications developed from scratch because many important tasks are handled by
the DBMS instead of being implemented by the application.
DISADVANTAGES OF DBMS:
Danger of a Overkill:
For small and simple applications for single users a database system is often not
advisable.
Complexity:
A database system creates additional complexity and requirements. The supply and
operation of a database management system with several users and databases is quite costly and
demanding.
Qualified Personnel:
`The professional operation of a database system requires appropriately trained staff.
Without a qualified database administrator nothing will work for long.
Costs:
Through the use of a database system new costs are generated for the system itself but
also for additional hardware and the more complex handling of the system.
Lower Efficiency:
A database system is a multi-use software which is often less efficient than specialized
software which is produced and optimized exactly for one problem
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