Data storage: database management system

The disadvantages of the file-oriented system are significantly improved by a database system. This section begins with the description about database approach in comparison to file-oriented system. After this, database system environment is described followed by the advantages & disadvantages of DBMS.

Data storage

Database approach

The following differentiates the main difference between the database system and file-oriented system.

As shown in above figure, in a database system, the data is managed by the DBMS. All access to the data is through the DBMS software. This provides an effective data processing. This contrasts to file-oriented system where application programs can directly interact with the data via operating system.

In file processing system, there will be different files to store different kind of data. And, these files might have been stored at different location in different disks. In DBMS, all data are stored in single database. Also, this database is kept at a single centralized location. This reduces redundancies. Also, it makes data management more efficient. With centralized database, it is possible to provide centralized control over all the data.

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Database system environment                     

A database system is a collection of database and a set of programs to manipulate data stored in a database. A database system provides basic functionalities like storage, manipulation and use of knowledge .

1.       Data

2.       Hardware

3.       Software

4.       Users

1.       Data:
Data is that the most vital component of the database system.
Data means known facts which will be recorded and have implicit meanings. for instance , a customer
can have data like customer id, name, address and get in touch with number.
Collection of related data is referred as database. In other words, database is a repository of related data.
For example, a database of a banking system involves collection of data about customers, employees,
accounts, loans, branches etc.
Such kind of data in a database are integrated and shared. Integrated data means they are correct and
consistent. Correct-ness suggests that data satisfies the integrity rules, such as balance should not be
negative. Consistency suggests that all the data stored in a database should be consistent. For example, an
account should not have a branch name which does not exist.
Depending upon the number of users interacting with the system, a database system can be single-users
interacting with the system, a database system can be single-user system or multi-user system. In multi-user
system, more than one users can access the database at the same time.

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2.       Hardware :

All the physical devices of a computing system are referred as hardware. A computing system can have number of various hardware like processor, memory, hard disk, monitor, key-board, mouse, printer, scanner, etc.

Data storage

From database system point of view, important hardware can be divided into two categories:

          1. The processor and main memory.                                                                          

                  Supports the execution of the database software.

                2. The secondary storage devices:

                    Used to store data of a system permanently.

                    Hard disks are the most widely used secondary storage devices now-a-days.

                    These include hard disks, magnetic tapes, compact disks, etc.

3.       Software:

Software provides the interface between users and database stored in physical devices. Application programs, DBMS software and operating systems form the software component here.

The operating system manages all hardware of the computer. The file system of the operating system provides interaction between other software components and hardware such as hard disk.

4.       User :

“Any one that interacts with a database in any form is taken into account as a database user.”

There are four main categories of the database users:

1.       Database administrator:

He/she is responsible for the paper functioning of the database system.

2.       Database designers:

Identify the info to be stored in database and styles structure of the database for a corporation .

3.       Application programmers:

Write application programs to develop database applications using some artificial language .

These users interact with the database in different manners depending upon their requirements.

Advantages of database management system :

Database management system contains centralized management and control over database. Also, DBMS software is used to provide interaction between application programs and database. Due to these, it provide many advantages. These advantages are given below.

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1.       Minimal data redundancy:

Due to centralized database, it is possible to avoid unnecessary duplication of information.

For example, all the information about bank customer can be kept centralized. Both accounts – saving also as current – can share this information. This prevents unnecessary duplication of customer information who has both sort of accounts.

This results in reduced data redundancy. Reduced data redundancy prevents memory wastage. Also, it eliminates extra time interval to urge required data during a large database. Less processing time improves the performance of the system.

2.       Improved data consistency:

Data inconsistency occurs due to data redundancy.

For example, consider that customers information is maintained separately for saving accounts and current accounts. Now if the address of some customer changes which has both sorts of accounts, it's possible that his/her address is updated for one account, leaving the opposite one because it is. This results in supply of wrong information and makes database inconsistent. With reduced data redundancy, such sort of data inconsistency are often eliminated. This leads to improved data consistency.

3.       Improved data integrity:

Data integrity means the info contained within the database is both correct and consistent. For this purpose, the info stored in database must satisfy certain sorts of constraints.
For example, balance in an account shouldn't be a negative value.

DBMS software provides different ways to implement such type of constraints. Also, it ensures that the data stored in database follows such constraints on its own. Application programs need not to worry about this.

This improves the data integrity in a database.

4.       Improved concurrent access:

Multiple users are allowed to access data simultaneously. This is for the sake of better performance and faster response.

As database is maintained centrally, data are often shared easily among multiple users.
Also, concurrent access to such data are often allowed under some supervision. This results in better performance of the system and faster response.

5.       Efficient data access:

DBMS utilizes a variety of techniques to retrieve data. Required data are often retrieved by providing appropriate query to the DBMS.
For example, information about all customers or from some particular city are often retrieved easily by providing appropriate query statements.
Thus, data are often accessed in convenient and efficient manner.

6.       Improved data sharing:

As database is maintained centrally, all authorized users and application programs can share this database easily.

7.       Guaranteed atomicity:
Any operation on database must be atomic. this suggests , it must happen in its entirely or not in the least . For example, a fund transfer from one account to a different must happen in its entirely.

It is the responsibility of the DBMS software to ensure such kind of atomicity. If any operation fails due to some problem such as system crash, then effects of the partially executed operation can be undone. Thus, in database systems, atomicity can be guaranteed.

8.       Improved security:

Database should be accessible to users during a limited way.
For example, a customer can check balance just for his/her own account.

DBMS software provides way to control the access to data for different users according to their requirements. Also, it's the responsibility of the DBMS software to stop unauthorized access to data. Thus, security can be improved.

Disadvantage of database management system :

DBMS provides a number of advantages over other database systems, such as file-oriented systems, as described in previous section. In spite of this, DBMS contains some drawbacks. 

1.       High cost:
It incurs high initial cost behind DBMS software. Also, hardware needs to be upgraded
according to requirements of the DBMS software.
Conversion from older file-oriented system to database system is additionally costly in terms of
cash also as time.

2.       Specialized manpower:
Database system requires specialized, skilled manpower to style & develop
database and to supply database administration services.
Also, due to rapid changes in database technology, this manpower needs to be trained and retrained
on regular basis.

3.       Security risks:
Database is kept centrally and can be used by multiple users remotely at same time.
This requires to authorize access to data among users to stop misuse of the confidential and
important data.

4.       Increased complexity:
It is necessary to know the wants of the organization and different sorts of users to style and
implement efficient database.

5.       Need of explicit backup and recovery:

As entire database is maintained centrally, it's must to supply efficient backup and recovery facilities. Else, any quite damage to the present database can affect the operations of the whole system.
Considering of these drawbacks, it becomes quite essential to make a decision whether to use database system or to use file-oriented system.
It is desirable to not use database systems if – database is straightforward & well-defined, needn't to vary frequently, and concurrent access among multiple users isn't required.