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Database Management System (DBMS)


DBMS is a collection of programs that help us to create and maintain a database. It is a general purpose software system that facilitates the processes of defining, constructing and manipulating databases for various applications. The data stored need not include every conceivable piece of fact about the enterprise. Usually, only the facts relevant to an enterprise are captured and organized. The purpose for the same is to provide information to support decision making at various levels, such as operational, management, etc. such a constrained area of focus is also often referred to as the domain or domain of attention/concentration. In another way, a database is an informational model of some domain.
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Advantages of Database Management System###
  1. A database pools the data for a series of applications so that the data is readily available from one central source to the persons authorized to access the information. This tends to promote the sharing of information so that the same basic information is used by more managers.
  2. Most types of database minimize data redundancy, which makes updating easier and less error - prone and saves processing effort and storage space.
  3. Program/file independence (P/FI), whereby programs do not contain direct references to data descriptions, permits reduced programming effort because the descriptions do not have to be programmed.
  4. P/FI speeds up program development because of the reduced programming effort needed.
  5. Preparation of special purpose reports, often a critical managerial need, can be accelerated several - fold.
  6. Fewer programs may be needed, since each can be access an entire database.
  7. Because of P/FI application programmes often do not need to be changed when record formats are changed. (The change is made only once in the data dictionary).
  8. A database often lets a file system evolve, rather than become obsolete, because additional data paths can be defined as needed.
  9. Less (or no) intermediate processing is required because the file integrates a database where cross - functional reports must be prepared. This decreases report preparation time and delay, reduces manual labor, and eliminate errors that occur during intermediate processing.
  10. It provides greater consistency of data in a database because most data elements occur in one place only and reports using those data elements are based on that one source.
  11. One transaction input can often update multiple database records, economizing on input effort.
  12. If the database has a query language (most do), managers can quickly develop their own relatively simple programs for queries or managerial analysis, without being dependent on data processing for this service.

Disadvantages of Database Management system

  1. Insufficient database expertise is perhaps the most serious disadvantage of DBMS. Database technology is complex, and few organizations have personnel with the necessary expertise to implement and manage database property.
  2. Database is usually responsible for a significant increase in the data processing of an organization and, resultantly, a commensurate increase in the cost of data processing.
  3. Increased hardware and software needs lead to a substantial increase in hardware and software cost. Direct access memory capability, greater communications capability (including communications software packages), and additional processing capacity are required with most database systems.
  4. Data security and integrity problems arise with the DBMS as many users have access rights to the database. The associative capabilities of a database make all data in the database potentially available for every year.
  5. Probably all but the first disadvantage will persist indefinitely, although it may be that, as technology becomes less costly, additional hardware and software costs will be less than the cost of utilizing more labor with conventional systems.

Components of the Database Management System

The database environment has the following components:
  1. Database Files - These files have data elements stored in the database file organization format. The database is created to balance the data management objectives of speed, multiple access paths, minimum storage, program- data independence, and preservation of data integrity. Basically, the DBMS tries to store data in a manner that facilitates rapid access while economizing on stage. The user is only concerned with the logical view of the data, that is, the relationships among data.

    For instance, a bank manager should know that the database contains the names, address and phone numbers of the customers as well as their recent savings, cheques, and loans histories. How exactly these data elements physically stored are not particularly important to the manager. Physical data descriptions are the concern of the Management Information System (MIS) department, which must select a database system that meets the needs of the users at a reasonable cost.
  2. Database Management System - DBMS is a set of complex systems software programs that manages the database files. The DBMS accesses the files, updates the records, and retrieves data as requested. The DBMS is also responsible for adding and deleting records, recognizing the database by reassigning storage space to make processing more efficient, and performing other housekeeping chores. The DBMS has the responsibility for data security, which is vital in database environment, since database is accessed by many users. The DBMS grants or withholds clearance to the application programs and terminal users for accessing the database files.
  3. Users - Users consist of both the traditional users like the accounting personnel, and application programmers, who are not traditionally considered to be users. The users interact with the database management system indirectly via application programes or directly via simple query language. This language enables the user to retrieve data in logical formats on an ad hoc basis. The user's interaction with the database management system includes the definition of the logical relationship in the database, the maintenance of data (including input), the changing and deletion of data, and the manipulation of data.
  4. Host Language Interface System - This is a part of the DBMS that communicates with the application programs. The host language interface interprets instructions in high - level language application programs, such as COBOL and BASIC programs, that request data from the files so that the required data can be retrieved. During this process, the Operating System of the computer interacts with the DBMS. The application programs do not contain information about the file. Thus, the program/file is independent of a database system, that is, there is nothing in the program that restricts its use to a particular data file.
  5. Application Programs - These programs perform almost the same functions that they do in connectional systems, but are independent of the data files and use standard data definitions. This independence and standardization make special purpose program development easier and faster. Application programs using the host language interface are usually developed by professional programmers.
  6. Natural Language Interface System - This query language permits on - line update and inquiry by users who are relatively unsophisticated about computer systems. This language is often termed English - like because instructions of this language are usually in the form of a simple command in English, rather than consisting of symbols and equations. Most of the commands of query language are pre - programmed and are activated when the user keys in combinations of English words to accomplish an inquiry task. Query languages also permit on-line programming of simple routines by managers who wish to investigate the status of projects which are in process by writing short programs rather than use only the existing query language commands. The natural language interface system may also facilitate managers or their assistants to develop elementary special reports.
  7. Data Dictionary - This is the centralized depository of information, in a computerized form, about the data in the database. The data dictionary contains the scheme of the database, ie, the name of each item in the database and a description and definition of its attributes. The data dictionary includes information about the data. With most database systems, the DBMS receives a request from a program for data and then accesses the database dictionary to determine whether the program has the right to receive the data it has asked for and to ascertain the location of the data in the database.
  8. On - line Access Terminals - These may be adjacent to the computer or thousands of miles away. These may be dumb terminals, smart terminals, or micro - computers.
  9. Output System or Report Generation - This provides routine reports, documents and special reports.

 

An illustration of Accounting Database

In the context of Accounting Database, we consider accounting transactions, support documents, accounts and employees in the following transactions.

 

Date

Transactions

Amount (Rs.)

October 10, 2007

Commenced business with cash

1,00,000

October 10, 2007

Loan received by cheque deposited into bank

50, 000

October 20, 2007

Purchased goods from RK & Co paid by Cheque No. 123451

25, 000

October 20, 2007

Sale made vide Invoice No. 1001 against cash

5, 000

October 20, 2007

Withdrew Cash from bank for office use

10, 000

October 20, 2007

Stationery purchased for cash from Raj Distributors

750

 

An accounting database that stores accounting transactions is shown below:

Details of employees in the context of the voucher approved by and prepared by:

 

Emp_id

Fname

Minit

L Name

Address

Phone No.

Super_Id

G001

Jaspal

Singh

Sahni

 

9071001951

 

G002

Lalan

Kumar

Jha

 

9018529339

G001

G003

Anil

Singh

Negi

 

9112059553

G002

G004

Ranveer

Kumar

Singh

 

9011047331

G003

 

Vouchers

V No.

Debit

Amount

Vdate

2007

Credit

Narration

Approved by

Prepared by

01

2200016

1,00,000

Oct. 10

1100001

Commenced business with cash

G001

G002

02

2200016

50,000

Oct. 10

1100005

Loan cheque deposited in bank

G001

G002

03

3300001

25,000

Oct.20

2200016

Purchased goods from R.K & Co

G001

G002

05

2200015

5,000

Oct. 20

4100001

Sales made

G001

G002

06

2200015

10,000

Oct. 20

2200016

Withdrew cash for office use

G001

G002

07

3300015

750

Oct. 20

2200015

Stationery Purchased

G001

G002

 

Detail of support of the Voucher:

V No

S No

Name

02

2

Cash deposit receipt

03

3

Purchase invoice No. with date

05

4

Sale cash memo no with date

06

2

Office cash requisition slip

07

3

Purchase invoice No. with date

 

Accounts code in respect to Debit and Credit column of the database.

Code

Name

Type

1100001

Capital Account

1

2200015

Cash Account

2

2200016

Bank Account

2

3300001

Purchases Account

3

4100001

Sales Account

4

1100005

Loan Account

1

3300015

Printing and Stationery Account

3

 

Type of Accounts according to their categories-

Cat _ Id

Category

1

Liabilities

2

Assets

3

Expenditure

4

Income





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