Introduction of Rdbms

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<p>Introduction to DBMS</p> <p>Database management has evolved from a specialized computer application to a control component of a modern computing environment. As such, knowledge about database system has become an essential part in computer science. Because in any organization, it requires accurate and reliable data for effective decision-making. In addition the Database Management exerts centralized control of the database, prevents fraudulent or unauthorized users from accessing the data, and ensures the privacy of the data. Data: Data is defined as the collection of meaningful facts which can be stored and processed by the computer. In other words, data is the material on which computer programs work upon. Data is raw facts or figures which can be processed. Data can be a number, letter of alphabets, words, special symbols and etc. but this information is unorganized.</p> <p>Information: Information is defined as the processed data that will help to make the further decision.Information will be generated after arranging the data into a suitable and meaningful form. The processed version of data is called information.</p> <p>Data</p> <p>Process</p> <p>Information</p> <p>File processing system: File based system is the manual database to keep the records in whichhuman being manages the database without the support of computer. This is the traditional approach to store the data. This system stores permanent records in the various files. In the file processing system whole data scattered into various paper and notebook. When we want to find some data, we have to search through the system from starting to end. The file based system was developed in response to the need of industry for more efficient data access and data storage. In the early system the records was stored in the file which is called file system.</p> <p>File:A file is a collection of letters, numbers and special characters which contain record.HIERARCHY OF DATABASE</p> <p>~</p> <p>1</p> <p>~</p> <p>Bit</p> <p>0.1</p> <p>Byte</p> <p>10101011(8-bits)</p> <p>Field</p> <p>(Attribute name like name, Age, Address)</p> <p>Record (One or more rows in a table)</p> <p>File</p> <p>(Table or collection of all records)</p> <p>Database</p> <p>(Collection of files or tables)</p> <p>E.g. Student (Database name) Filed name or attribute name</p> <p>Personal table name</p> <p>Academic (Table name)</p> <p>Name John Ramesh</p> <p>Father Name Albert Suresh</p> <p>Age 24 18</p> <p>~</p> <p>2</p> <p>~</p> <p>Record</p> <p>Disadvantages of file processing system:</p> <p>Duplicacy of data: In manual system repetion of data create duplication. Duplication is wasteful as it requires additional storage space. Data duplication creates the problem of data inconsistency. There is possibility of information getting duplicated, this redundancy is storing same data multiple times leads to higher costs and wastage of space. Integrity Problem: The problem of integrity is the problem of ensuring that the data in the database is accurate. Several types of constants must be imposed in order to enter the right type of data in the database. But in file system it is not possible to apply the constraints. Security Problem: Data stored in the file system must be safe from outsider. Any unauthorized user can destroy the data and it leads to data inconsistency. In file processing system security constraints are not easy to enforce. Data dependence: In files data is stored separately in each file. File system leads data dependence as when the data changed in one file, the corresponding data in other have also to be changed. Difficult to share data: File system gives the sharing problem because data is stored in different files uses different format. Which are not compatible with each other. Multiple users cannot share a single file. Difficult to get quick response: In file system, user cant get quickly the required output. To find the data user have to search the whole file.</p> <p>Disadvantages of file processing system:</p> <p>~</p> <p>3</p> <p>~</p> <p>Concurrent problem: When more than one user need to access the same file at a simultaneously, is known as concurrent problem. When more than one user at the same time read and update andf modify the files it will create the problem as it may have inaccurate data. Enable to represent data modeling of real world: The file system approach has the inability to design a database which shows the basic entities, relationships and models.</p> <p>What is the database?A database is a collection of related information stored so that it is available to many users for different purposes. The content of a database is obtained by combining data from all the different sources in data in an organization. So that date are available to all users and redundant data can be eliminated or at least minimized. A computer database gives us some electronic filing system, which has a large number of ways of cross-referencing, and this allows the user many different ways to reorganize and retrieve data. A sales base can handle business inventory, accounting and filing &amp; use the information in its files to prepare summaries.</p> <p>Characterstics of data in the database: </p> <p>Data in the database are shared by different users and application. Data in the database are permanent. Data should be secured and protected from unauthorized users. Whenever more than one data elements in a database represent related data the data values should be consisted.</p> <p>Data should not be duplicated in the database. Data should be independent in the database.</p> <p>~</p> <p>4</p> <p>~</p> <p>Data should be well organized. It should be flexible to change. Data should be correct. Data should be available when needed</p> <p>Significance of database:Database plays an important role in the real world as we were used database in the manual system of keeping the records where large number of files was used to store the data in the database. To solve the problems found in following examples we need database. Consider the example of majority of people whose phone number changed from five digits to six digits then it would be difficult to change all the phone numbers from the telephone directory as we need to change all the phone number. To overcome this situation we can create a new directory. With this option the job will become more complex. It is quite clear from the examples that traditional approach works at great accuracy if there is less number of data to be processed. The manual approach does not work well if we have to process larger amount of data. To overcome the problem of the manual system the database approach is used.</p> <p>Why a database?Handling of a small shops database can be done manually but if you have a large data base and multiple users than in that case you have to maintain computerized database. The advantages of a database system over traditional, paper-based methods of record keeping will perhaps make it more apparent. Here are some of them. 1. 2. Compactness: No need for possibly voluminous paper files. Speed: The machine can retrieve and change data faster than a human being.</p> <p>~</p> <p>5</p> <p>~</p> <p>3.</p> <p>Less drudgery: Much of the sheer tedium of maintaining files by hand is eliminated.</p> <p>Mechanical tasks are always better done by machines. 4. Accuracy: Accurate, up-to-date information is available on demand at any time.</p> <p>Database Management SystemThere can be a database, which store newspaper articles, magazines, books and comics. There is already a well-defined market for specific information for highly selected group of users on almost all subjects. MEDLINE is a well-known database service providing medical information for doctors and similarly WESTLAW is computer based information service catering to the requirements of lawyers. The key for making all this possible is the manner in which the information in the database is managed. The management of data in database system is done by means of a generally purpose software package called a database system is done by means of a general purpose software package called a Database Management system. The Database Management system is the major software component of a database system. Some commercially available DBMS are Ingress, ORACLE, and Sybase. A Database Management system, therefore, is a combination of hardware and software that can be used to set up and monitor a database, and can manage the updation and retrieval of database that has been stored in it.</p> <p>Advantages of using DBMSThe DBMS has a number of advantages as compared to traditional file system. The DBA must keep in mind these benefits or capabilities during designing databases, coordinating and monitoring the DBMS. Following are the advantages of using DBMS:Controlling redundancy: Centralized control of data by the DBA avoids unnecessary duplication of data and reduces the storage space. In traditional file processing, every user maintain its own files. Each user independently creates their own data so therefore most of the data is stored twice or more.</p> <p>~</p> <p>6</p> <p>~</p> <p>Minimizing data inconsistency: Data inconsistency exists when different copies of the same data exist in different places. By controlling the data redundancy, the data consistency is obtained. Restricting unauthorized access: Each DBMS provide security and authorization. Database system requires you to login and then process the data. Each user can process the data according the rights given by the DBA.</p> <p>Advantages of using DBMSImproved data access: The DBMS provide quick answer to queries of the user. The DBMS quickly sends back the answer of the query. Providing compatibility with programming languages: DBMS provide the compatibility with the programming languages like C, C++, JAVA etc. Data administrator: Data administrator means managing and organizing data from a central point by the DBA. Administration provides a user to easily access the data according to its requirement. Enforcing integrity constraints: DBMS enforce integrity constraints on the data. For example, before inserting salary information for an employee, the DBMS can check that the data department budget is not exceeded. Providing backup and recovery: Each DBMS provide the facilities for recovering from hardware or software failure, such as disk crash, power failure, software errors.</p> <p>Disadvantages of using DBMSAlthough there are many advantages of DBMS, the DBMS may also have some minor disadvantages. These are: Cost of hardware and software: A processor with high speed of data processing and memory of large size is required to run the DBMS software. The cost of these hardware and software are very high.</p> <p>~</p> <p>7</p> <p>~</p> <p>Cost of data conversion: When a computer file-based system is replaced with a database system, the data stored into data file, must be converted to database file. It is very difficult and costly method to convert data of data files into database. You have to hire database and system designers. So a lot of money has to be paid for data conversion. Cost of staff training: Most DBMS are often complex systems so the training for users to use the DBMS is required. The organization has to be paid a lot of amount for the training of staff to run the DBMS. Appointing technical staff: The trained technical persons such as database administrator application programmers, data entry operators etc. are required to handle the DBMS. Companies have to pay high salaries to these persons. Database damage: In most of the organization, all data is integrated into a single database. If database is damaged due to electric failure or database is corrupted on the storage madia, then you valuable data may be lost forever. Privacy and security is reduced: When information is centrally stored and is made available to remote users, the possibilities of destruction of data is often more than traditional system.</p> <p>Database administratorA database administrator(DBA) is a person who is responsible for the management of a database. DBA is a person or group of persons who implements the policies of an organization. He is responsible for authorizing access, monitoring database use, providing satisfactory response time, backup and recovery from the system failure. DBA has all the powers of the database.</p> <p>Duties of the DBAThe main duties of the DBA are as under: Installation of new software: It is basic the job of the DBA to install new version of DBMS software, application software, and other software related to DBMS administration.</p> <p>~</p> <p>8</p> <p>~</p> <p>Data dictionary management: Management &amp; control of data dictionary is an important role of the DBA.DBA creates the data definition, data validation rules, documentation of data dictionary and etc.</p> <p>Duties of the DBA</p> <p>Scheme defination: The creation of the original database scheme. This involves data storage and definition language technique. Storage structure and access method definition: Writing a set of definition used by the data storage and language compiler. Define integrity rules: DBA is responsible for defining integrity rules for the database. These rules help to maintain database security. Configuration of hardware and software with the system administrator: DBA works with the system administrator to take decision about hardware and software settings. Security administration: DBA has to monitor and check DBMS security. This involves adding and removing users and provide permission to them. Data analysis:DBA has to analyze the data stored in the database and he has to give recommendation relating to performance and efficiency of that data storage. Database design: A DBA has to design database on each level. DBA creates the policy about internal, conceptual, and external level.</p> <p>Components of the DBMSA database system is composed of four components; Data Hardware</p> <p>~</p> <p>9</p> <p>~</p> <p> Software Users Which coordinate with each other to form an effective database system.DBMS</p> <p>Application program</p> <p>Application program</p> <p>Data and programApplication program database users</p> <p>Application program users</p> <p>Data: It is a very important component of the database system. Most of the organization generate,store and process large amount of data. The data acts a bridge between the machine and the user. User can directly access the data from the machine. Data may be of different types: </p> <p>User Data: The user data is stored in rows and column in the form of tables. Metadata: A description about the structure of the database is known as Metadata. It means</p> <p>data about data. It stores in data dictionary.</p> <p>Hardware: The hardware consists of any kind of physical storage device like secondary storage devices like disks(hard disk, zip disk, floppy disk), optical disks(CD-ROM), magnetic tapes etc. on which data is stored together with the Input/Output devices (mouse, keyboard, printers), processors, main memory etc. which are used for storing and retrieving the data in a fast and efficient manner.</p> <p>~</p> <p>10</p> <p>~</p> <p>Components of the DBMS</p> <p>Software: The software acts as a bridge between the users and the database. Software interacts with the users, application programs,...</p>