Introduction to Dbms
Data : Word 'Data' is originated from the word 'datum' that means 'single piece of information.' It is plural of the word datum. Data is a collection of a distinct small unit of information. It can be used in a variety of forms like text, numbers, media, bytes, etc. it can be stored in pieces of paper or electronic memory, etc.
Database : A database is an organized collection of data, so that it can be easily accessed and managed.You can organize data into tables, rows, columns, and index it to make it easier to find relevant information. So, now we can say that database is a collection of related data and data is a collection of facts and figures that can be processed to produce information.The main purpose of the database is to operate a large amount of information by storing, retrieving, and managing data.
Database Management System : A database management system stores data in such a way that it becomes easier to retrieve, manipulate, and produce information.
Functions of DBMS :
- Data abstraction and independence.
- Data security.
- A locking mechanism for concurrent access.
- Robust data integrity capabilities.
- Logging and auditing of activity.
- Simple access using a standard API.
- Uniform administration procedures for data.
Characteristics of Dbms System
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Real-world entity : A modern DBMS is more realistic and uses real-world entities to design its architecture. It uses the behavior and attributes too. For example, a school database may use students as an entity and their age as an attribute.
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Relation-based tables : DBMS allows entities and relations among them to form tables. A user can understand the architecture of a database just by looking at the table names.
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Better Data Transferring : Database management creates a place where users have an advantage of more and better managed data.
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Data Security : As number of users increases data transferring or data sharing rate also increases thus increasing the risk of data security.A Database Management System (DBMS) provide a better platform for data privacy and security policies thus, helping companies to improve Data Security.
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Less redundancy : DBMS follows the rules of normalization, which splits a relation when any of its attributes is having redundancy in values. Normalization is a mathematically rich and scientific process that reduces data redundancy.
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Minimized Data Inconsistency : Data inconsistency occurs between files when different versions of the same data appear in different places.
For Example, data inconsistency occurs when a student name is saved as “John Wayne” on a main computer of school but on teacher registered system same student name is “William J. Wayne”, or when the price of a product is $86.95 in local system of company and its National sales office system shows the same product price as $84.95.
So if a database is properly designed then Data inconsistency can be greatly reduced hence minimizing data inconsistency.
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ACID Properties : DBMS follows the concepts of Atomicity, Consistency, Isolation, and Durability (normally shortened as ACID). These concepts are applied on transactions, which manipulate data in a database. ACID properties help the database stay healthy in multi-transactional environments and in case of failure.
File System : A File Management system is a DBMS that allows access to single files or tables at a time. In a File System, data is directly stored in set of files. It contains flat files that have no relation to other files (when only one table is stored in single file, then this file is known as flat file).
DBMS vs. File System
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DBMS
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File System
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DBMS is a collection of data. In DBMS, the user is not required to write the procedures.
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File system is a collection of data. In this system, the user has to write the procedures for managing the database.
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DBMS gives an abstract view of data that hides the details.
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File system provides the detail of the data representation and storage of data.
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DBMS provides a crash recovery mechanism, i.e., DBMS protects the user from the system failure.
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File system doesn't have a crash mechanism, i.e., if the system crashes while entering some data, then the content of the file will lost.
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DBMS provides a good protection mechanism.
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It is very difficult to protect a file under the file system.
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DBMS contains a wide variety of sophisticated techniques to store and retrieve the data.
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File system can't efficiently store and retrieve the data.
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DBMS takes care of Concurrent access of data using some form of locking.
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In the File system, concurrent access has many problems like redirecting the file while other deleting some information or updating some information.
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RDBMS : Relational Database Management System (RDBMS) is an advanced version of a DBMS system. It came into existence during 1970's. RDBMS system also allows the organization to access data more efficiently then DBMS.RDBMS is a software system which is used to store only data which need to be stored in the form of tables. In this kind of system, data is managed and stored in rows and columns which is known as tuples and attributes. RDBMS is a powerful data management system and is widely used across the world.
DBMS vs RDBMS
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RDBMS |
| DBMS applications store data as file. |
RDBMS applications store data in a tabular form. |
| In DBMS, data is generally stored in either a hierarchical form or a navigational form. |
In RDBMS, the tables have an identifier called primary key and the data values are stored in the form of tables. |
| DBMS does not apply any security with regards to data manipulation. |
RDBMS defines the integrity constraint for the purpose of ACID (Atomocity, Consistency, Isolation and Durability) property. |
| DBMS uses file system to store data, so there will be no relation between the tables. |
in RDBMS, data values are stored in the form of tables, so a relationship between these data values will be stored in the form of a table as well. |
| DBMS does not support distributed database. |
RDBMS supports distributed database. |
| DBMS is meant to be for small organization and deal with small data. it supports single user. |
RDBMS is designed to handle large amount of data. it supports multiple users. |
| Examples of DBMS are file systems, xml etc. |
Example of RDBMS are mysql, postgre, sql server, oracle etc. |
Database Architecture
DBMS architecture helps in design, development, implementation, and maintenance of a database. A database stores critical information for a business. Selecting the correct Database Architecture helps in quick and secure access to this data.
- 1 tier Architecture : The simplest of Database Architecture are 1 tier where the Client, Server, and Database all reside on the same machine. Anytime you install a DB in your system and access it to practise SQL queries it is 1 tier architecture. But such architecture is rarely used in production.
- 2 tier Architecture : In two-tier architecture, the Database system is present at the server machine and the DBMS application is present at the client machine, these two machines are connected with each other through a reliable network as shown in the above diagram.Whenever client machine makes a request to access the database present at server using a query language like sql, the server perform the request on the database and returns the result back to the client. The application connection interface such as JDBC, ODBC are used for the interaction between server and client.
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3 tier Architecture : In three-tier architecture, another layer is present between the client machine and server machine. In this architecture, the client application doesn’t communicate directly with the database systems present at the server machine, rather the client application communicates with server application and the server application internally communicates with the database system present at the server.
An important objective of the three-tier architecture is to provide data independence, which means that the upper levels are unaffected by changes in the lower levels. There are two kinds of data independence :
- Logical Data Independence :
- Logical data independence refers characteristic of being able to change the conceptual schema without having to change the external schema.
- Logical data independence is used to separate the external level from the conceptual view.
- If we do any changes in the conceptual view of the data, then the user view of the data would not be affected.
- Logical data independence occurs at the user interface level.
- Physical Data Independence :
- Physical data independence can be defined as the capacity to change the internal schema without having to change the conceptual schema.
- If we do any changes in the storage size of the database system server, then the Conceptual structure of the database will not be affected.
- Physical data independence is used to separate conceptual levels from the internal levels.
- Physical data independence occurs at the logical interface level.
For Introduction to DBMS part 2 Click Here
For more Delhi Technical University(DTU) CSE-IV Database Management System Lab Experiments Click Here
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