Functions of DBMS

Friday, May 23, 2008 by Ankit Goyal

Functions of DBMS

DBMS free the programmers from the need to worry about the organization and location of the data i.e. it shields the users from complex hardware level details.

DBMS can organize process and present data elements from the database. This capability enables decision makers to search and query database contents in order to extract answers that are not available in regular Reports.

Programming is speeded up because programmer can concentrate on logic of the application.

It includes special user friendly query languages which are easy to understand by non pro¬gramming users of the system.

The various common examples of DBMS are Oracle, Access, SQL Server, Sybase, FoxPro, Dbase etc.

The service provided by the DBMS includes:

Authorization services like log on to the DBMS, start the database, stop the Database etc.
Transaction supports like Recovery, Rollback etc,
Import and Export of Data.
Maintaining data dictionary
User's Monitoring

Advantages Of DBMS

by Ankit Goyal


The DBMS (Database Management System) is preferred ever the conventional file processing system due to the following advantages:

1. Controlling Data Redundancy - In the conventional file processing system, every user group maintains its own files for handling its data files. This may lead to

Duplication of same data in different files.
Wastage of storage space, since duplicated data is stored.
Errors may be generated due to updation of the same data in different files.
Time in entering data again and again is wasted.
Computer Resources are needlessly used.
It is very difficult to combine information.

2. Elimination of Inconsistency - In the file processing system information is duplicated through¬out the system. So changes made in one file may be necessary be carried over to another file. This may lead to inconsistent data. So we need to remove this duplication of data in multiple file to eliminate inconsistency.

For example: - Let us consider an example of student's result system. Suppose that in STU¬DENT file it is indicated that Roll no= 10 has opted for 'Computer'course but in RESULT file it is indicated that 'Roll No. =l 0' has opted for 'Accounts' course. Thus, in this case the two entries for z particular student don't agree with each other. Thus, database is said to be in an inconsistent state. Sc to eliminate this conflicting information we need to centralize the database. On centralizing the data base the duplication will be controlled and hence inconsistency will be removed.

Data inconsistency are often encountered in every day life Consider an another example, w have all come across situations when a new address is communicated to an organization that we deal it (Eg - Telecom, Gas Company, Bank). We find that some of the communications from that organization are received at a new address while other continued to be mailed to the old address. So combining all the data in database would involve reduction in redundancy as well as inconsistency so it is likely to reduce the costs for collection storage and updating of Data.

Let us again consider the example of Result system. Suppose that a student having Roll no -201 changes his course from 'Computer' to 'Arts'. The change is made in the SUBJECT file but not in RESULT'S file. This may lead to inconsistency of the data. So we need to centralize the database so that changes once made are reflected to all the tables where a particulars field is stored. Thus the update is brought automatically and is known as propagating updates.

3. Better service to the users - A DBMS is often used to provide better services to the users. In conventional system, availability of information is often poor, since it normally difficult to obtain information that the existing systems were not designed for. Once several conventional systems are combined to form one centralized database, the availability of information and its updateness is likely to improve since the data can now be shared and DBMS makes it easy to respond to anticipated information requests.

Centralizing the data in the database also means that user can obtain new and combined information easily that would have been impossible to obtain otherwise. Also use of DBMS should allow users that don't know programming to interact with the data more easily, unlike file processing system where the programmer may need to write new programs to meet every new demand.

4. Flexibility of the System is Improved - Since changes are often necessary to the contents of the data stored in any system, these changes are made more easily in a centralized database than in a conventional system. Applications programs need not to be changed on changing the data in the database.

5. Integrity can be improved - Since data of the organization using database approach is centralized and would be used by a number of users at a time. It is essential to enforce integrity-constraints.

In the conventional systems because the data is duplicated in multiple files so updating or changes may sometimes lead to entry of incorrect data in some files where it exists.

For example: - The example of result system that we have already discussed. Since multiple files are to maintained, as sometimes you may enter a value for course which may not exist. Suppose course can have values (Computer, Accounts, Economics, and Arts) but we enter a value 'Hindi' for it, so this may lead to an inconsistent data, so lack of Integrity.

Even if we centralized the database it may still contain incorrect data. For example: -

• Salary of full time employ may be entered as Rs. 500 rather than Rs. 5000.
• A student may be shown to have borrowed books but has no enrollment.
• A list of employee numbers for a given department may include a number of non existent employees.

These problems can be avoided by defining the validation procedures whenever any update operation is attempted.

6. Standards can be enforced - Since all access to the database must be through DBMS, so standards are easier to enforce. Standards may relate to the naming of data, format of data, structure of the data etc. Standardizing stored data formats is usually desirable for the purpose of data inter¬change or migration between systems.

7. Security can be improved - In conventional systems, applications are developed in an adhoc/temporary manner. Often different system of an organization would access different components of the operational data, in such an environment enforcing security can be quiet difficult. Setting up of a data¬base makes it easier to enforce security restrictions since data is now centralized. It is easier to control who has access to what parts of the database. Different checks can be established for each type of access (retrieve, modify, delete etc.) to each piece of information in the database.

Consider an Example of banking in which the employee at different levels may be given access to different types of data in the database. A clerk may be given the authority to know only the names of all the customers who have a loan in bank but not the details of each loan the customer may have. It can be accomplished by giving the privileges to each employee.

8. Organization's requirement can be identified - All organizations have sections and de¬partments and each of these units often consider the work of their unit as the most important and therefore consider their need as the most important. Once a database has been setup with centralized control, it will be necessary to identify organization's requirement and to balance the needs of the competating units. So it may become necessary to ignore some requests for information if they conflict with higher priority need of the organization.

It is the responsibility of the DBA (Database Administrator) to structure the database system to provide the overall service that is best for an organization.

For example: - A DBA must choose best file Structure and access method to give fast response for the high critical applications as compared to less critical applications.

9. Overall cost of developing and maintaining systems is lower - It is much easier to re¬spond to unanticipated requests when data is centralized in a database than when it is stored in a conventional file system. Although the initial cost of setting up of a database can be large, one normal expects the overall cost of setting up of a database, developing and maintaining application programs to be far lower than for similar service using conventional systems, Since the productivity of program¬mers can be higher in using non-procedural languages that have been developed with DBMS than using procedural languages.

10. Data Model must be developed - Perhaps the most important advantage of setting up of database system is the requirement that an overall data model for an organization be build. In conven¬tional systems, it is more likely that files will be designed as per need of particular applications demand. The overall view is often not considered. Building an overall view of an organization's data is usual cost effective in the long terms.

11. Provides backup and Recovery - Centralizing a database provides the schemes such as recovery and backups from the failures including disk crash, power failures, software errors which may help the database to recover from the inconsistent state to the state that existed prior to the occurrence of the failure, though methods are very complex.