Introduction to Database System Explain given database concept. 2 Explain overall structure of DBMS. Describe architecture of database. [1.0] INTRODUCTION logy and its application in all spheres of modern society, «With the rapid growth in computing technol databases have become an integral component/part of our everyday life. day life that involve interaction with a database, for We encounter several activities in our day-to- example, bank database to withdraw and deposit money, movies database for booking of tickets, bus, air or railway reservation databases for booking of tickets, supermarket goods database to keep the inventory etc. «In fact, databases and database management systems have become essential for managing for business, governments, banks, universities and every other kind of human endeavor. + Thus, they are a critical component of today's software industry, to support a daunting task to solve the problems of managing huge amounts of data that are increasingly being stored. «Data is the cornerstone of any modern software application, and databases are the most common systematic way to store and manage data used by applications. ‘A database is an organized collection of structured information or data while A database management system (DBMS) allows to access and interact with the underlying data in the database. + Together, the data and the DBMS, along with the applications that are associated with them, are referred to as a database system, (often shortened to just database). + The goal of the DBMS is to provide a convenient and effective method of defining, storing and retrieving the information stored in the database. DATABASE CONCEPTS In today’s age of information explosion, where people/user are bombarding with data, getting the right information, in the right amount, at the right time in not easy task. So, managing of this huge amount of data become an essential thing. * A database is an organized collection of inter-related data, stored and accessed electronically using computer systems. * Databases are important because they allow organizations to store, organize, and access large amounts of data efficiently and effectively. + A DataBase Management System (DBMS) is a software or program that allows access/retrieval of data that contained in database. a)Database Management System i ive method of * The objective of the DBMS is to provide a convenient and ae net i ‘iy Tetrieving the information stored in the database, The da S collectively known as database system, i * Adatabase is an organized electronic collection of ae eed 15a system that eng i 1m a database, Store, modify and retrieve data in an organized way fro * Databases a collection of related data and data is a collection of facts and figures 4 processed to produce information. : ‘ Addatabase management system stores data in such a way that it becomes easier tg manipulate, and produce information, 1m any organization, data isthe basic resource needed to run the organization, datum, which means a single piece of information. The data can be defined as “a set of isolated an can be anything such as text, number, is data, ‘When the data is processed and Data is the \d unrelated raw facts with an implicit ‘Meanin mages, sound, video et. For example, ‘Amar’ 4g Converted into a meaningful and useful form known as For example, ‘Amar is 18 years old and he isa student’ is information, Data and Closely related and are often used interchangeably, Databaseis a collection of related data and data isa collection of facts and figures that ‘Processed to produce information, * A database system simplifies the tasks of managing the data and extracting useful informatio timely fashion, 7 A database isa logical grouping of data. A database system is an integr along with the details ofthe inte ated collection of pretation of the data, Database is a collection of data. The Database contains information ab * Adatabase (DB), the desired information. A datal Properties of Database: elements (facts) representing real 2 Adatabase isa logically collection of data with some meaning, ‘database is designed, built and populated with data fora Specific purpose, Databases are structured according to a specific data model, such as relational, network, object-oriented and so on, A database is logical, coherent, and internally consistent.abase Management stem a Introduction to Database System, patabases are organize by fiels, records and fle. These are described briefly a follows: 1 Fields: tis the smallest unit ofthe data that has meaning tots users and is also called data tem Fr data element. Name, Address and Telephone number are examples of fllds, These are represented in the database by a value a, Records: records coleton of logically related elds and each eld possesses fixed number of bytes and is of fixed data type. 4, Files: A file is a collection of related records. es of Databases: ‘with the explosion of wel databases to more advance ‘There are many different types of databases. Th how the organization intends to use the data. 1 elational Databases: Relational databases became dominant in the 1980s, tems ina relational database are organized as a set of tables with columns and rows. Examples of relational databases include MySQL, Oracle, and Microsoft SQL Server. Relational database technology provides the most efficient and flexible way to access structured information. 2, Object-oriented Databases: Information in an object-oriented database is represented in the form of objects, as in object-oriented programming, Examples of objectoriented databases include, GemStone/S, ObjectDB and so on. 4. Distributed Databases: A distributed database is stored and managed across multiple servers, rather than on a single central server. It is designed to provide faster access to data and to improve the scalability and reliability of the database, Examples include distributed NoSQL database options like Cassandra, ScyllaDB, and MongoDB. 4. NoSQL Databases: ANoSQL (Not SQL or Not Only SQL) or nonrelational database, allows unstructured and semi-structured data to be stored and manipulated. Examples of NosQl databases include MongoDB, Cassandra, and Couchbase. There are several types of NoSQL DBMS: pen source Databases: An open source database system is one whose source code is open. source; such databases could be SQL or NoSQL databases. Open-source databases are open to modifications and free to use, Examples include MySQL. Cloud Databases: A cloud database is a collection of data, either structured or unstructured, that resides on a private, public, or hybrid cloud computing platform. Cloud databases are accessed over the internet and can be used by multiple users or applications, providing a flexible and scalable way to store and manage data. Example include, Microsoft Azure, Amazon Web Servi p and cloud technologies, databases have evolved from traditional relational xd types of databases such as NoSQL. e best database for a specific organization depends on databases (also known as autonomous databases) are cloud: automate various tasks in the DBMS like security, backups, management tasks traditionally performed by database ad . Multi-model Databases: These databases provide a single database model types. Examples include, MarkLogic Server, |. Document/JSON Databases: These databases are a NoSQL stor JSON documents. A document database is a type of NoSQL d documents instead of columns and rows. JSON is a native data, These documents can be grouped together into Examples include, Amazon DocumentDB, MongoDB, 10, Graph-oriented DBMS: This type of NoSQL dat relationships, Examples include GraphDB and Neo4j.4 Introduction to Database [1.1.3] Components of Database + Adatabase consists of four components as shown in Fig. 1.1 ‘© Fig. 1.1 shows following components of a database: 1. Data Item is a distinct piece of information and is explained in the previous section. 2. Relationships represents a correspondence between various data elements. 3. Constraints are the predicates that define correct database states, 4. Schema describes the organization of data and relationships within the database. [1.1.4] Database Management System (DBMS) Is.23] + ADatabase Management System (DBMS) is an integrated set of programs used to create and maintain Fig. 1.1: Components of Database a database. * The primary objective of a DBMS isto provide a way to store and retrieve the database information in convenient and efficient manner. + A Database Management System (DBMS) is a software system that allows user to define, manipulate and process the data in a database, in order to produce meaningful information. + Examples: 1. Manufacturing Company: Which stores data such as product id, name, price etc. 2. Bank: Which stores customers banking data such as cust name, balance, acc_no. etc. 3. Hospital: Which stores patient data such as Patient ID, Patient_name, Admit date, Discharge date etc. 4. University: Which stores student data such as student.name, college_name, address, courses, staff-details etc. * Some of the popular relational database management systems include Microsoft Access, Microsoft SQL Server, MySQL and Oracle. Queries in this book can be executed using Oracle Express Edition which is open source. * DBMS is defined as, “the software system that allows users to define, create, maintain and control access to the databast OR * A DBMS is, “a software system that allows user to define, manipulate and process the data in a database, in order to produce meaningful information’ + The DBMS is hence a general-purpose software system that facilitates the processes of defining, constructing and manipulating databases for various applications. © Defining @ database involves specifying the data types, structures and constraints for the data to be stored in the database Constructing the database is the process of storing the data itself on some storage medium that is controlled by the DBMS. © Manipulating a database includes such functions as querying the database to retrieve specific data, updating the database to reflect changes in the mini-world, and generating reports from the data, * So, in general, user can write programs or queries; DBMS use the database stored on storage devices and gives meaningful information.anagerent System 1s Menage Se Introduction to Database System patabase the database system is ilstrated in the Fig. 1.2, The main objective of a DBMS isto provide a convenient and effective method of defining, storing, retrieving and manipulating the data contained in the database. Users/Programmers Database = System | Application Programs/Querieg DBMS Software ‘Software to Process. ‘Queries / Programs ‘Software to Access: sored Data eee ee ‘Slored Database Defnion Fig. 12: Simple Database System There are many DBMS like MySQL, PostgreSQL, Microsoft Access, SQL Server, FileMaker, Oracle, RDBMS, 4BASE, Clipper, FoxPro and so on. «DBMS acts as an interface between the application program and the data stored in the database, (Refer Fig. 1.3) End users Database structure Application request i ‘Customers. | DBMS (Database” Single |” Management [ tovoices | |_End-user Beem el Yoo | ata cndusers ___Avpteation| pata | [Pues] | i request — ee Fig. 13: Interface between Application Program and DBMS + Examples of DBMS include MySQL, Oracle, DB2, SQL Server and so on. ‘The basic functions of DBMS are: 1. Tostore data in a database. 2, To organize the data. 3, To control access of data. 4, To protect data Le., provide security. Characteristics of DBMS: ‘L._ Users File Approach: In file processing, each user defines and implements the files needed for a specific application, therefore more storage space is required. In DBMS, a single database is maintained that is defined once and then is accessed by various users.Database Management System. if A an 2. Self-describing Nature of DBMS: One of the most fundamental ae Et it that the database system contains not only the database itself but als efiitog i database (metadata). oa ie Programs and Data: DBMS access programs are tai Independent specifi files. The structure of data files is stored in catalog separately from t access prog (orogram-data independence). in file processing, if any change in structure of file is made all programs that access this file have to be changed. i 4 Muliple Views: A database supports multiple views of data. A view is a subset of the data which i defined and dedicated for particular users of the system, Multiple users inthe right have different views of the system. Each view might contain only the data ‘ser or group of users. 5. Sharing of Data: Current database systems are designed for multiple users, ‘any users to access the same database at the same time. This sharing of data DBMS not in files. & Enforcement of Integrity Constraints: Database management systems must provide the abil to define and enforce certain constraints to ensure that users enter valid information maintain data integrity. A database constraints a restriction or rule that dictates what can entered or edited in a table. 7 Backup and Recovery Facilities: Backup and recovery are methods that allow to Protect the da From loss The database system provides a separate process, fom that of a network backup, fo Packing up and recovering data. If hard drive fils and the database stored on the hard drive Zot accessible, the only way to recover the database is from a backup. [1.1.5] File System vs DBMS 3, of interest That is, they 4s possible only A file is @ named collection of related information. A file system is that st of system software that Provides services to users and applications in the use of files, A DEMS is a software system that allows user to define, manipulate and process the data in a database, in order to produce meaningful information" —in this section we study concepts of file processing system and DBMS, File System Earlier file processing system was used to store the database. The database was stored in a typical operating system file File system also knows as conventional file system is the oldest way of keeping the data files organizec on the drives, In file processing system (Refer Fig. 1.4) the records are stored in separate files, Each file is called @ flat file To access the data from these flat files, variou: Is programs are written, So, that the system provides fruitful information to the end user. Actually, speaking the work is tedious, Because if user wants simple change in the resultant database, lot of changes are needed in the application programs ig. 1.4: File Processing System Characteristics of File Systems: 1 File system isa group of fils that stores the data of an organization, 2 mn fil system file is independent of one another,Management System a. Introduction to Database System 4, Each fle in filesystem i a fat file nile system files ar designed using programming languages like COBOL, C, C++ and so on. ach fli file ystem contains the processed information for one specific function fig 15 shows an example of traditional le processing sjtem ofan organization, Al functional areas in the organization creat, processes and disseminates its own fils, ve files suc as Sales department and Accounting department et. generat separate files and do not communicate with each other. Personnel ane pes Department Department oe ‘Application pplication pom rogram a Be ee Fig. 1.5: Example of Traditional File System tem lost its flexibility and shows many As system becomes more complex, file processing sys limitations or disadvantages. Some of them are listed below: |. Data Redundancy and Data Inconsistency: Im a file processing system each application has its own redundancy in stored data, with waste in storage space. Redundancy is unnecessary duplication of data. For example, if accounts department and registration department both keep student name, number and address. pata inconsistency occurs when there is data redundancy. Data redundancy occurs when the data file/database file contains redundant - unnecessarily duplicate data, Data inconsistency means different copies of the same data are not matching, That means different versions of same basic data are existing, This occurs as the result of update operations that are not updating the same data stored at different places. Difficulty in Accessing Data: ‘The file processing system do not allow to access data in convenient and efficient way. It is not easy to retrieve information using a conventional file processing system. Convenient and efficient information retrieval is almost impossible using conventional file processing. private files. This can often lead to system. ‘As the data was scattered in different files and whenever, need arises different application programs were written by different programmers in different formats, }. Data Isolation: As the data is scattered in various files and files may be in different formats, writing new application programs to retrieve the data is very difficult, |. Data Integrity: The data values stored in the database must satisfy some consistency constraints. This describes the problem of ensuring that the data in the database is accurate. Enforcing data integrity ensures the quality of the data in the database.Database Management System 1 * For example: The balance field value must be greater than 5009. ¥ rogram code in file processing systems. But in database we can along with definition itself. 5. Atomicity Problems: + Ifany failure occurs in the system the transactions which are executing shoul should not, so that database remains in consistent state. © For example: If a transaction of transferring money from account X to account ¥ is in process, system failure occurs the money from account X to ¥ should get transferred or should neg transferred. File processing system do not ensure such atomicity. 6. Concurrent Accessing Problems: ‘© If multiple users are updating the same data simultaneously it will result in inconsistent data staze, file processing system itis very difficult to handle this using program code. This results in con: ‘access anomalies, + To improve the performance of the system, multiple transactions must get executed concurrs ‘Multiple transactions may be updating the same data concurrently. In such case the data may in inconsistent state. 7. Security Problems: + Enforcing security constraints in file processing system is very difficult as the application programs are added to the system in an ad-hoc manner. + The data in the DBMS should be secured. Only authorized person should be able to modify the data Security should be maintained at different levels which were not possible in file processing system. [x52] Database System (DBMS Environment) + The DBMS software together with the database is called a database system. The database system can be defined as, “an organization of components that define and regulate the collection, storage, management and use of data in a database”. + A database system is a system whose overall purpose is to record and maintain information. Is simple terms, Database + DBMS Software = Database System. + A database system consists of four major components as shown in Fig. 1.6 ie., Data, Hardware, Software and Users. ‘+ Addata file is a single disk file that stores related information on a hard disk. Datatase management system (OBMS). Application programs, Fig. 1.6: Components of Database Systemee ~ Introduction to Database System ponents of Database System: Data: formation or real fact which can be recorded and have implicit meaning. ‘A data is collection of in 2 svt whole data inthe database system s stored ina single database and this data inthe database are sri shared, Gharing of data means Individual plees of data in the database is shared among ferent users and every user can access the same piece of data but may be for different purposes) ang integrated, integration of data means the database can be function of several distinct files with redundancy controlled among the files). Hardware: The hardware consists of d with other devices. the secondary storage devices like disk, where the database resides together Software: risa ayer or interface of software exists between the physical database and the users. This layer i called the DBMS. 1 requests from the users to access the database are handlled by the DBMS. Users: ‘The users are the people interacting with the database system in any way. ‘he four types of users interacting withthe database are Application Programmers, Online users, End users (naive users) and Database Administrator (DBA). Various functions of DBMS are listed below: 1. Data Definition: The DBMS must be able to accept data definitions (external schemas, the conceptual schema, the internal schema, and all associated mappings) in source form and convert them to the appropriate object form. Data Manipulation: The DBMS must be able to handle requests from the users to retrieve, update, or delete existing data the database, or to add new data to the database. In other words, the DBMS must include a Data Manipulation Language (DML) processor component. . Data Security and Integrity: The DBMS must monitor user requests and reject any attempt to violate the security and integrity rules defined by the DBA. Data Recovery and Concurrency: The DBMS ~ or else some other related software component, usually calied the transaction manager ~ must enforce certain recovery and concurrency controls. . Data Dictionary: The DBMS must provide a data dictionary function. The dictionary might should be integrated into the database it defines, and thus include its own definition. It should certainly be possible to query the dictionary just like any other database, so that, for example, itis possible to tell which programs and or users are likely to be affected by some proposed change to the system Performance: It goes without saying that the DBMS should perform all of the functions above as efficiently as possible. + Fig. 1.7 shows database system of an organization, Personnel Department 6, rf otabase Management System Advantages of DBMS over File Processing ¢ listed below: Farious advantages of DBMS over file system are listed 4 Teh a database system data can be easily shared by different users. In Dpyg a a oe controlled and can be shared by all authorized users. Ses se sys grity means that the data con Empro Integrity: In database systems, data integrity 1 . a Soeesaeae and consistent. The centralized control of DBMS allow ads sn be incorporated to provide data integrity. Data Consistency: In DBMS the problem of inconsistent data is automatically solveg controlling the redundancy. 4 Controlled Redundancy: In DBMS, the duplication of data can be carefully controlled, that me se syetem is aware ofthe redundancy and it assumes the responsibility for propaga the 3. Efficient Data Access: The DBMS utilizes different sophisticated techniques to access the ston data very efficiently. §. Program Data Independence: The DBMS provide an independence between the file system application program, that allows for changes at one level of the data without affecting others 7. Enforcement of Standards: In DBMS, data being stored at one central Place, standards can be enforced by the DBA. This ensures standardized data formats to facilitate data tra betwee lems. 8 Improved Security: Database security means protecting the data contained in the database fra unauthorized users. In DBMS the DBA ensures that Proper access procedures are follo Proper authentically schemes for access to the database and additional checks cing access to sensitive data, 8. Improved Backup and Recovery Facility: Through backup and recovery subsystem of DBMS Provides the facilities for recovering from hardware or software failures. 10. Concurrency Control: The DBMS are designed to manage simultaneous (concurrent) access of P Base by many users. They also prevent any loss of information (loss of integrity) due to these concurrent accesses, 11. High Data Quality: The quality of data in database systems is very high as compared 10 12. Minimal Program Maintenance: In a traditional file system, high maintenance efforts are ‘d. These are reduced to minimal in database systems due to independence of data and programs 13. Economical to Scale or Low Cost: In DBMS, the operational data of an organization is stored ina v Gatabase. The application programs that work on this data can he built with very less cost roe tha gona filesystem. This reduces overall costs of operation and management of that leads to an economical scaling M4. Increased Programmer Productivity and Reduced Development Time: The DBMS provides aul fac and these functions allow the Programmers to concentrate on the specific functionality required by ‘ 5 i 'y required by the users without Worrying about the implementation details. This increases the overall prod y and oat Productivity of the programmer and also Teduced the development time 15. Good Data Accessibility and c The database systems provide query languages ra ni that allow the users to ask ad-hoc queries took te nel peated 16 Lamp without the regurementtownte applica Programs, : uage Interface: DBMS provide a language support for definition and ‘manipulation of data. Responsiveness:aroperers SEE epaduction ts Sacase System hardware is crease the ditional fle ch more and it depends on nce costs of hardware. ;pplications in an organization. system requires a consensus on mm and has additional annual maintenance ‘om old Sle-system to new database system is and the security of sensitive data stored s are among the major disadvantages of DBMS because cplenity, it can slow down query speed and increase Comparison between File System and DBMS: | Sr.No. Terms { File Processing System | Database Management System Scope PC-based small systems. | ‘Mini-mainframe based large systems. » 2 Cost Less price as small systems. | Relatively expensive as bigger | | | systems. | 3. | Nooffiles Less number of files used. | ‘More number of files used. { | created | 4. | Noof Users | single user system. | Multiple user system. } 5. | ‘Major Features | Data redundancy and inconsistency | Data is independent and non- 1 occurs. redundant. | 6. _| Data Access Data access is difficult. | Data access is efficient. [> Teoncurrency | Concurrent access toa fileisnot | Concurrent access and crash | possible. recovery possible.eg hd saith "ie 14 Ditterence between File Based System and Database Management System [216] Applications of DBMS ing sectors: omer information, accounts, loans and banking transactions. ations and schedule information. Airlines were among the first to ust disturbed manner-terminals situated around the world accessed the em through phone lines and other data networks. a Universities: For mi 1 information, course registrations and grades. 1. banking Fat For cu Airlines System: For re:13 Introduction to Database System . credit card transactions: For purchases on credit cards and generation of monthly statements. . Telecommunications: For keeping records of calls made, generating monthly bills, maintaining ratanees on prepaid calling cards and storing information about the communication networks : For storing information about holdings, sales and purchase of financial 6. Finance Syste! instruments such as stocks and bonds. +, sales Management System: For customer, product and purchase information. F. Manufacturing: For management of supply chain and for tacking production’ of fers in factories, inventories of items in warehouses/stores and orders for items ¢, Human Resources Management: For information about employees, salaries, payroll taxes and penefits and for generation of paychecks. 10. Web Based Services: For taking web users feedback, responses, resource sharing et tegration of heterogeneous information sources (for example, catalogs) for hopping, booking of holiday package, consulting a doctor, etc. es use databases for course registration, result, and other 11, E-commerce: business activity such as online sl 42. Education: Schools and colleg: information. Data Abstraction f 7 database management system is a collection of interrelated files and a set of programs that allow users to access and manipulates these files. ‘A main purpose of a database management system is to provide users with an abstract view of the Gata, That isthe database system hides certain details of how data are stored and maintained. Data hiding the implementation details from the end users. DBMS uses the same principle means it data is stored on the secondary storage device in DBMS. hides the complex details of how the Data abstraction is refers to, "the hiding of certain details of how the data are stored and maintained”. Database stored at complex level is kept hidden from the users at three different levels. The architecture for DBMS is divided into three general levels as shown in Fig. 1.9 external or view level, conceptual of logical level, and internal or physical level. External Level { ez 22, 5-24] ((ndividual user view) Conceptual Level (Community user view) Internal LevelPhysical level (Storage view) Fig, 1.9; Three Levels (External, Internal and Conceptual) of DBMS Let us see levels of data abstraction: External Level: External level also known as view level. The highest level of abstraction describes only part of the entire database. External level concerned with the way individual users see the data. External Level: © ishighestlevel. © describes part of the database for a particular group of users. © can have many different views of a database, for example, tellers in a bank get a view of customer accounts, but not of payroll data.Database Management System 114 Introduction tata 2. Conceptual Level: Conceptual level also known as logical level. The next-higher level of describes what data are stored in the database, and what relationships exist among those day logical level thus describes the entire database in terms of a small number of relatively structures. Conceptual Level: is next highest level of abstraction. © describes what data are stored. © describes the relationships among data. © database administrator level. 3. Internal Level: Internal level also known as Physical level. The lowest level of abstraction de how the data are actually stored, The physical level describes complex low-level data st detail. Internal leve © how the data are stored. © lowest level of abstraction. © complex low-level structures described in detail. * There are three levels of data abstraction as shown in Fig. 1.10 with example. Bi we ° Branch Code Type=Byto(6) Orfset=6 ee ‘Salary Type=Byte(6), Offset=35. { ' User? User? User3 —— | tee |_Mewt | [[Mew2)] [ivewsl] | i { ' Conceptual ‘Conceptual { Level schema 1 Bee i ' interna Hl intemal ima = | ' { Physical data | |storesémplyed Leng © #8 ength= Organisation Database | [Code Type Byo(, fst, ' i { { ' I (@) Levels of Data Abstraction Fig. 1.10 + Example: Let us say we are storing customer in © Atphysical level these records can © At the logical level these records can types, their relationship among each generally work at this level because th © Atview level, user just i user just interact screen, they are not aH ‘hidden from them, *Y are aware of such things about database systems, system with the help of GUI and ent ; te the “wire of how the data is stored and what data is oe ma deathLas laticaais Data Independence means the property to change the overall logical or physical structure of the data ms view of data i, the views created for users does not Data independence without changing the application progra have any change. Data independence is del one level without having t Data independence means that 0 strategy of data There are two I independence. Physical Data Independence cal data independence is the ability to modify the physical schema without causing application ined as, “the characteristics of a database system to change the schema at 10 change the schema at the next higher level”, fhe application is independent of the storage structure and access levels of data independence namely, physical data independence and logical data Phys programs to be rewritten. Modifications at the physical level are occa change the physical storage/level without a new changes are absorbed by mapping techniques. th his physical layout and organization of data may be changed without changing either the overall Jogical structure of the data or the application programs. For example: We can add extra fields ie, new fields to the database without disnarbing the old records; say in emp table. char address [20] isadded. Actually, in'C’or in any programming language if we do so, the program should also be changed. Bot in DBMS it is not required. Because of the Data independence facility, the change is automatically sionally necessary to improve performance. It means we ffecting the conceptual or external view of the data. The reflected in secondary storage device. 1.1.8.2] Logical Data Independence Togieal data independence is the ability to modify the logical schema without causing application program to be rewritten. Modifications at the logical level are necessary whenever the logical structure of the database is altered (For example, when money-market accounts are added to banking system). Im logical data independence, the overall logical structure of data may be changed without changing application program. This is hard to achieve because application programs are usually dependent on logical structure of the data For example: To achieve this, attributes from different tables are considered and, on those attrsbutes, query is written, Here, attribute name, table names are properly selected and written, otherwise result may not appear with the required format. See [oes] [Beez] Dera] ~~ [reed == Lopeal data independence Logical level Physical data independence Physical level Database fies Fig. 1.11:Data IndependenceDatabase Managé ven 16 * Data independence is advantageous inthe database environment, since it ome i change i level of the database without affecting other levels, These changes are abs between the levels. ad thevelove architecture, + Fig. 1.11 shows relationship between data independence and three-level DBMS architecture, Comparison between Logical and Physical Data Independence: a Introduction to Databay may Sr.No. Physical Data Independence Logical Data Independence 1, | Itis ability to modify the internal schema of a database without the need to modify the conceptual schema of the database, Itis the ability to modify the conceptual schema of a database without the need to modify the external schema, Changes in the physical level are usually done to improve the overall performance of a database. Change in te logical level are usually done modify the logical organization of the data, The conceptual schema insulates the users from changes in physical storage of data, The users are shielded from changes in the logical structure of the data or changes in the choice of relations to be stored. Teleaves the conceptual (logical) schema ‘unaffected by changes made to the physical scheina, which in turn also leaves the exterhal schema unaffected, Itleaves the external (view) schema and methods for accessing the information unaffected by changes made at the conceptual schema, Examples: Changing the internal data structures or Creating additional access Paths for retrieving the same data more efficiently, etc Examples: Adding or deleting a field froma Tecord type or Modifying the existing constraints, etc Application programs do not depend much on the physical structure of the data, Hence | itis relatively easier to achieve this, Application programs are highly dependenton the logical structure of the data and it isa Instance and Schema * Database is schema is database structure and the co instance is also called database st 1.1.9.1] Database Schema ‘The overall description of the dat * / Actually, DBMS has a three level architecture and Schemas in the database. These are given below: 1. Physical Schema: [tis + Aschema is defined as, The schema diagram is used to show the databi mn of information stored inthe database ata particular, prante of the database, The overall design ofthe database isc description of a database. straints that should hold on the database fate (or occurrence), ‘abase is called as the database schema, at the lowest level. ie., at Physical level, it the next or intermediate level i.e. highest level ie, at the View “an outline or a Plan that descril ase schema, A schema diagram displays only some Gifficult job to achieve this. (nstance of time) moment is called an alled the database schema, Database schema includes description of the accordingly there are three different types of » at Logical level. level. bes the records existing at a particular level”437 Introduction to Database System STUDENT_ADDRESS Roll. No, | Name Address Place PIN ‘STUDENT_MARKS Roll.No. | Subject_| Exam_Date Marks. Fig. 1.12: Schema Diagram 1.9.2 Database Instance mn the information insert or delete. Databases change over time whe! ‘formation stored in the database at a particular moments called as an instance of The collection of it the database. For example, the i mnstances of STUDENT_ADDRESS table are as shown in following table. ‘STUDENT_ADDRESS. Roll_No. | _Name Address Place PIN a1 Amar ‘A-2/7, JanakPuri Pune 110012 02 Deepa B-5, Saket Pune 110014 03 Kiran G8, Rajouri Garden Pune 110036 pifference between Instance and Schema: “Sr.No. Instance Schema 7, | the actual content of the database ata | The overall design of the database is called particular time is called database database schema. | instance, ZT itdeseribes the data structure ofthe | Tt Gescribes the contents of the database. | database. 3. _| Instance state is called extension. Schema is also called intension. “4. | instance changes every time the The database schema changes very infrequently. database is updated. 5 [an instance is analogous to the value of A schema is analogous to the value of a variable in a variable in a program. a program at any execution point, 1.1.10| Codd’s Rules yhas relational capabilities for managing The codi's rules can be applied to any DB system that merely Management Systems’ had stored data in the database. in number, The rules are numbered from zero to twelve. » Dr. E. F. Codd, also known to the wol propounded 12 rules which are in-fact 13 ides by all his twelve rules. Till now, only few fondly called ‘EF.Codd’s Twelve According to him, a DBMS is fully relational if ital databases abide by all the eleven rules. His twelve rules are Commandments’. rid as the ‘Father of DatabaseSES: 4 _—— Database Management System 1 * Dr. Edgar F. Codd's Twelve rules are explained below: Rule 0: Foundation Rule: any relational database RDBMS or advocated to be a RDBMS should through its relational capabilities. Rale 1: Rule of Information: Relational Databases show! a eyes i aay Sa Tables are relations in Relational Database Management hn hie a OF meta-data, itis important to store the value as an entity in the — x Rule 2: Rule of Guaranteed Access: The use of pears ser bee — ally by using g Every data entity which is atomic in nature should be accessed logi 5 Eitan cs aan table, primary key represented by a specific row value column name represented by attribute value. Owe Rule 3: Rule of Systematic Null Value Support: Null values are completely eg Tela databases. They should be uniformly considered as ‘missing aie ion’. Null values independent of any data type. They should not be mistaken for blanks or zeroes oxy strings. Null values can also be interpreted as ‘inapplicable data’ or ‘unknown information» Rule 4: Rule of Active and online relational Catalog: In the Database Management 5) Jexicon, ‘metadata’ is the data about the database or the data about the data. The aca, online catalog that stores the metadata is called ‘Data dictionary’. The so-called dictionary is accessible only by authored users who have the required Privileges and query languages used for accessing the database should be used for accessing the data’ data dictionary. Rule 5: Rule of Comprehensive Data Sub-language: A single robust language should be able to define integrity constraints, views, manipulations, transactions and authorizations. If the database allows access to aforementioned ones, itis violating this rule. Rule 6: Rule of Updating Views: Views should reflect the updates of their respective base tables Tot aiSs. A view Isa logical table which shows restricted data. Views generally make the data readable but not modifiable. ‘Views help in data abstraction. Rule 7: Rule of Set level insertion, Update and Deletion: A single operation should be sufficient to retrieve, insert, update and delete the data. Rule 8: Rule of Physical Data Independence: Batch and end user operations are logically separated from physical storage and respective access methods, Rule 9: Rule of Logical Data Independence: Batch and end users can change the database schema itor recreate the applications built upon it. id store the data in the form of : Any row should obey the securit and inte; constraints: Imposed. No special privileges are applicable, ¥ il Overall Structure of DBMS. Storagt 119 Introduction to Databate System query Processor: A query processor contains following components: ra () DMLPrecompiler: It translates DML statements in a query language into low level instructic 7 that query evaluation engine understands. lons Italso attempts to transform user's request into an equivalent but more efficient form. (Embedded DML Pre-compiler: It converts DML statements embedded in an application program to normal procedure calls in the host language. ‘The Pre-compiler must interact with the DML ‘compiler to generate the appropriate code, (iii), DDL Interpreter: It interprets the DDL statements and records them in a set of tables containing meta data or data dictionary. (iv) Query Evaluation Engine: It executes low-level instructions generated by the DML compiler. je Manager: It provides the interface between the low-level data stored in the database and and queries submitted to the system. application programs dlIntegrity Manager: I tests for te satisfaction of integrity constraints checks (Authorization an the authority of users to access data. (i Transaction Manager: It ensures that the database remains in a consistent state despite the system failures and that concurrent transaction execution proceeds without conflicting. ii File Manager: It manages te allocation of space on disk storage and the data structures used to represent information stored on disk. Gx) buffer Manager: It is responsible for fetching data from disk storage into main memory and deciding what data to cache in memory. Naive “aplication ‘Sophisticated Database programmers: users: administrator plication | pplication | “erace ‘ferane on Serene File manager Indices | Sesto——————— in kins cs Database Management System 120 Introduction to Database System 3. Database Users: (s-221] (v) Database Manager or Storage Manager: It is a program module which provides the interface between low level data stored in the database and the application programs and queries submitted to the system. Following are responsibilities of Database Manager: (a) Interaction with the File Manager: Actual data is stored in the file system, The database manager translates the various DML statements into low level file system commands, This database manager is responsible for actual storing, retrieving and updating of data in the database. (®) Integrity Enforcement: Consistency constraints are specified by database administrator. But the responsibility of database manager is to enforce, implement or check those constraints. (© Security Enforcement: It is the responsibility of database manager to enforce the security requirements. (@) Backup and Recovery: It is the responsibility of database manager to detect system failures and restore the database to a consistent state. (©) Concurrency Control: Interaction among the concurrent users is controlled by database manager. The storage manager or database manager is thus responsible for: Storing the data, Retrieving the data, and © Updating of data in the database. Data Structures: Following data structures are required as a part of the physical system implementation. @ Data Files: It stores the database. (i) Data Dictionary: It stores meta data (data about data) about the structure of the database, (iii) Indices: Provide fast access to data items that hold particular values. (iv) Statistical Data: It stores statistical information about the data in the database. This information is used by query processor to select efficient ways to execute query. DBMS provide an environment to store and retrieve information. On the basis of interaction with the system, users are differentiated to following types. © Patabase administrators (DBAs) are the primary users who manage and control the Gatabase. They are responsible for the overall functioning of the database system. Their tasks include data management, performance tuning, security enforcement, backup and recovery, and oubleshooting. DBAs have the highest level of access and control over the database. © Application programmers are users who interact with the database through a programming language. They write database queries and codes to create, retrieve, update, and delete data. They use languages like SQL (Structured Query Language) to interact with the database. © End-users are the people who interact with the database through a graphical user interface (GUD. They use the database for various Purposes like retrieving information, updating records, or generating reports. 2 3 & 3 5 = 3 5 = SLa Introduction to Database System specialized users are sophisticated users who write specialized database appli ata icati not fit into the traditional data-processing framework. Among these spelt id cae aided-design systems, knowledge-base and expert systems ete, computer Database designers are the users who design the structure of database which includes tabi indexes, views, triggers, stored procedures and constraints which are usually enforced before a9 database is created or populated with daa, Helshe controls what data must be stored and hove the data items to be related. Naive users are unsophisticated users who interact with the system by involving one of the permanent application programs that have been written previously. DATABASE ARCHITECTURES The database architecture is a framework in which the structure and/or design of the DBMS is described, + Database system an manipulated and retrieved from the database. The overall design of the Database Management System (DBMS) depends on its architecture, DBMS hitecture describes how the database is designed and the way users access the database. res that the functions (define, create, manage, organize ; providing a stable and reliable platform for data jtecture outlines the methodology by which data is stored, organized, A well-designed database architecture & and control) are performed seam nagement. Two-tier Database Architecture We can maintain and manage the DBMS with the applications of different architectures depending on what way the user is connected to the database system and accessing the database. As a DBMS is not always available directly by the user or an application. These architectures are defined according to tiers ie, the number of levels in the DBMS’s structure determines which category the DBMS architecture belongs to. Atieris a physical unit where a process or a program is executed. Database servers, application servers, clients, etc., are a few examples of tiers. Two tier architecture consists of only two levels Database (server) and client, (See Fig. 1.14). The 2-tier Architecture is based on a client-server system. In The twottier architecture, the applications on client-side interact directly with the database present at the server-side, This interaction between client and server uses Application Program Interface like ODBC (Open DataBase Connectivity) and JDBC (Java DataBase Connectivity). In Fig. 1.14 shows various clients are sending the request to the database server and the database server executes the request given by client and sends the result of the request only back (response) t0 server, Client acon Program (View) Response: Client Fig. 1.44A ———— Database Management System — Je (0 COMMUNIEAL * Intwortier DEMS architecture the use and the DBMS which i response (0 DIN taney aquest tothe database management sytem an thet sen he respons 0 Advantages of Two-tier Architecture : etrieval and update, 1. The client has direct access to the database, allowing for fast ot ae _ 2. The twortier architecture is simple ancl easy to understand, as it in Po namely, the client and the server: aerate S The client software can be deployed on individual workstations, making IC easter (0 yyy maintain and update. sng f ‘A The twotier architecture can be easily sealed by adding more clients or upgrading the hardware, é The main problem of two-tier architecture is the server cannot respond multiple request SAMO thy 38.8 result it causes a data integrity issue, Three-tier Database Architecture ‘The three main components of the threeschema architecture describe three levels of abstrag Within the database system namely external, conceptual and internal. ‘The three levels within the database architecture represent different views of the data When a Sravests data by writing a database query, they use the structures contained in their view of database. * The user's request must be converted from one of the external views to the conceptual view of Gatabase and then tothe internal view of the database, The process of expressing one level int of another is called a mapping. “a Spping converts the contents of one level into another, for example, a mapping between conceptual level and the external level converts the contents ofthe conceptual level into one or emernal level views. * When the user requests data from the database using an external schema descri ‘the conceptual schema and then to the internal schema. * The main purpose of the three-schema from other users. * Users should be able to view the data in the fo iption it is mapped architecture is to separate each user's view of the dat rm that best suits their needs, The same informat may be viewed in more than one way. Users are not concerned with how the database has been Physically implemented but instead are interested only in the content ofthe database, * The external schema also “hides the rest ofthe database from that user group”, In an external view, 4 user will only see the entities, relationships and attributes that are of particular interest to them, * The conceptual schema is a description of what is in the database, The conceptual schema describes the content of the whole database. Its purpose is to hide the details of how the database has be implemented in a particular database management system, * The conceptual schema presents a hi; attributes. It will also describe the sect * The internal schema describes how schema as “describing the physical internal schema as “the phy: * The internal schema will de the data, * The purpose of the internal schema is to allow the database administrator to achieve the optimal implementation of the database, for example, the maximum query Performance or the minimum storage space usage. igh-level view of the database using entities, relationships and. ‘rity and integrity constraints of the whole database, the database is implemented. Elmasri etal defines the internal Storage structure of the database”, Connolly et al defines the sical representation of the database on the computer”, scribe the set of operating files and index Structures that are used to storese Management System 123 Introduction to Database System ‘he internal schema will describe the mapping between database relations and fle, the types of sngexes used, the allocation of disc blocks tothe database, the method of record placement for each relation and any data compression or encryption techniques to be used. Me ss — Exteria/conceptual mapping Conceptual Level ‘Conceptual Schema Conceptualinternal mapping Internal Level Internal Schema eee Stored Database Fig. 1.15: Three Level Architecture of Database System End users. dvantages of Three-tier Architecture: 4, The three-tier architecture can be easily scaled by adding more servers or upgrading existing servers, improving performance, and ensuring high availability. 2. The three-tier architecture easier to secure data and control access to the database. ‘The architecture makes it easier to maintain and upgrade the system, as changes can be made to one tier without affecting the others. 1.3 | DATA MODELS ‘A data model is a collection of conceptual tools for describing data, its relationship, data semantics and data constraints, A data model consists of: 1, Anamed logical unit ie,, record type and data item. 2, Relationship among these logical units. 3, Data item is logical unit of data and record type is collection of data items, We can say, a data model is description of a container in which data and its methods of retrieving data are available, Actually, it provides abstraction of database application. efinition and Types of Data Models: ‘A data model is a collection of concepts that can be used to describe the structure of database model is a specification describing how a database is structured and used. ‘A model defines the method of storing and retrieving data. Data modeling helps: of the meaning of the data, ‘A data model is a way of representing data and its inter-relationship. Data the database design process. ‘The process of applying a data model theory to create a data modeling. Data modeling isa way to structure and organize data2 Physical Data Models: These data models describe how data is stored in the computer. It re [1.3.1] Relational Data Model Derabase Management Syste 1s Definition of Data Model: + Adatabase modelis, “a type of data model that determir fondamentally determ: er data can be * A data model is defined as, “an integrated collection of concep eta, relationships between data and constraints on the data in an 0 of Data Models: a: ae 1.16 shows categories of data models and the models are described belo an 1. Object Based Data Models: These data models are used to describe = A Be Bi lew of a database. It is used to describe logical data structure. There are two subtypes: 4 © Entity Relationship Model: It is high level data model based on the fact of real v = This consists of collection of basic objects called as entities and the relationship anons thea Gi) Object Oriented Model: This model is based on collection of objects. Each object has its methods. Actually the value stored for a object and methods are grouped into a logical unit as dass. s the logical structure of a da ed, and manipulated", information like record structures, record ordering and access paths. For example, the Unify model and the Frame memory model. Record Based Models: These data models are used in describing data at the logical and view These models are so named because the database is structured in fixed format records of Data Models ae =] | Sas 1.16: Types of Data Models The relational model was formally introduced by Dr. E.F. Coda of tables to represent both data and the relati As collected. A real et mn [at fle composed of a columns (attributes) and Tows (values for columns). The secu’ Of the tables contain information about the table. ' - The ror resent occurrences ofthe thing” represented by the table. wo A data value is stored in the inter “section of a row and column, Each named ; ; column has a domain, Which isthe set of values that may appear in that column, oanam This allows database st system, it model. In network model data is represented represented by links. The records are or Network model consists of set type corresponds to the 1. Ease of Design can Re CUSTOMER CustID | Cust.Name | Cust.clty a1 Mina | Pune 02 Rina Satara 03 Bina Bharamati CUSTOMER-AMT CustJD_| Account.No*} o1 1224 02 3424 For example: In a database, CUSTOMER table and ACCOUNT table are the two tables relationship between these two tables have been shown by a third table, where i Bal ae ae a from both the table is taken together. So a new table called CUSTOMER-AMT is dl ane ERCAMT Is forme a0 System ‘ACCOUNT *AccountNo | ino | Amt 1214 10,000 wus 5000 Fig. 1.17: Representation of Relational Model vantages of Relational Model: 1. Easier to Design, Implementation, M independence are pr administration and u 2, Simple: It is sim them 3, Structural Independence: This model has structural covided by the relational model which makes databasé sage much easier and simpler than the othe ipler model as it frees the designers from the ac to concentrate on the logical view of the database. 1 independence, ie. changes made in the jer models. rructure do not affect the DBMS's capability to access data. 4. Better Query Capability: This model provi facilities. It uses Fourth-Generation Languages 5, No Anomalies: This model does not su operation is very simple, easy and systematic \dvantages of Relational Model: ‘esult in Bad Design: As the relational databas in the development and implementation of poorly design‘ can result ‘management systems. . Performance Degradation: As the si this model like system slowdown, per! 3, Hardware Overheads: The RDBMS nee implementation complexities and the phys 1.3.2 | Network Data Model Tin late 1960s, the DataBase Task Group (D! ale fer from insert, up network diagram in which record type corresponds to relatlonship represented by links. ze of the database increases, several problet formance degradation and data corruption. .ds comparatively powerful cal data storage details from the users. 3BTG) formalized network model. Fig. 1.18 sh aintenance and Usage: Both data as well as structural e design, maintenance, sual physical data storage details. ides very powerful, flexible and easy-to-use query (AGL) like SQL that makes ad-hoc queries a reality. date and delete anomalies. The retrieval e is an easy-to-design and use ied database sms may creep in hardware as it hides the jows network by collection of records and the relationship among the data is. ‘ganized as a collection of arbitrary graphs. the entity sets and1.26 Database Management System i i nts the related where ACCOUNT table information is stored. Each link information represe! mae ACCOUNT CUSTOMER at yunt.No. | __ Amt Cust _| Cust.Name | Cust.city Account Ne a1 Mina Pune Link o— [J 1 10,000 o2 Rina Satara nw] 03 Bina __| Bharamati ee Fig. 1.18: Representation of Network Model 3424 5000 Advantages Network Model: 2. Simplicity: This model is simple and easy to design just as hierarchical data model. 2. Data Integrity: This model, no member can exist without an owner. A ser must therefore fir define the owner record and then the member record. This ensures the data integrity. 5 Capable of Handling More Relationship ‘Type: This model handles 4:1, 1M and relationships which helps in modeling the real-world applications. 4. Data Independence: This model is better than the hierarchical model in isolating the progran from the complex physical storage details 5._ Database Standards: This model is based on the universal standards formulated by the DBTG, Disadvantages Network Model: 1. Lack of Structural Independence: Making structural modifications to the database is difficult in this model as the data access method is navigational. 2 Not User-friendly: This model is not a design for user-friendly system and is a highly oriented system, 3: Operational Anomalies: Since, network model contains operational anomalies like update, insert, delete etc, 4. System Complexity: As all the Tecords are maintained using pointers, so the whole database structure becomes very complex. Hierarchical Data ModelManagement System 427 Introduction to Database System In nierarchical model data is viewed asa collection of relations (Segments) that frm a hierarchical relation. A hierarchical relation i Iierarchical tre by logical association (inks), rantages Hierarchical Model: A. simplicity: The database is based on the hierarchical structure, the relationship between the «layers is logically (conceptually) simple, Thus, the design of a hierarchical database is defined as, "a collection of relations that are connected together as a various simple. a, ata Integrity: The hierarchical model is based onthe parentcild relationship, there i alwaysa tink between the parent segment and the child segments under it.The child segments are always ‘automatically referenced to its parent, this model promotes data integrity because of parent/child relationship. 4. Eificiency: This model i a very efficient one when the database contains a large number of 11N relationships (one-to-many relationships). pata Sharing: Because all data are held in a common database, data sharing becomes practical in this model. «vantages Hierarchical Model: 4, inflexibility: A hierarchical database lacks flexibility. The changes in the new relations or segments often yield very complex system management task. 2, No Standards: The implementation ofthis model does not confirm to any specific standard. 4, Implementation Complexity: Although the hierarchical database model is quite complex to implement. The database designers should have very good knowledge ofthe physical data storage characteristics. 4. Implementation Limitation: format as required by the hierarchical model 5. Database Management Problems: If any changes in the database structure of a hierarchical database, then it need to make the necessary changes in all the application programs that access the database. Thus, maintaining the database and the applications can become very difficult. It also takes time, so it becomes time consuming. 6. Operational Anomalies: This model suffers from the insert, retrieval operation is complex and asymmetric. parison between Hierarchical Model, Network Model and Relational Mod Many of the common relationships do not conform to the 1:N update and deletion anomalies. The Sr. Hierarchical Network Relational No. Model Model Model 1. | Thismodel is based on tree | This model is based on graph | This model is based on (hierarchy) structure. (tree of records) structure. mathematical concept of relations (tables). 2. | Structural independence is | Structural independence is | It offers structural missing. missing. independence. | 3. | Hierarchical database Network database consists of | Relational database consists of consists of collection of _ collection of records, tables (relations) and data is records, connected to each | connected to each other by _| stored in tabular form. other by links, links. Contd...Introduction to 28 Database Management System a tne rai " cated | Queries are easy a 4. | Queries are easy to write | Queries are more nn ae than other moa than in network model but_| to write than hierarchical more complicated than relational model. relational model, 7 ri ta access is non. 5. | Data access is navigational. | Data access is navigational. Data acc ‘ ‘ navigational. ai & | Itis easy to understand and | 1 offers more flexibility than i cde a a jerarchical model. ; ae netooand herr network data model, aaa 7. |The hierarchical structure | The network structure is more | The relational structure ig is asymmetric and is a symmetric than hierarchical | more symmetric than ne major drawback that leads _| structure. and hierarchical structure, to unnecessary complications for the user. 8. | Itisdifticult to access Data accessingismore easy | Data accessing is easy and Values at lower level, than hierarchical model. simple than other models, 8: | Information is replicated in | it offers more data consistency | If offers more data consi Hierarchical model which | than hierarchical model than other two models, leads to inconsistency and Wastage of storage space, 10. | Teuses Dif though coBoL. | ituses copoL based Ituses SQL. commands, 4. What is meant by file pro 5. Enlist various applicatio 6. Define the following terms: (@ Data and i) Database, Explain how ma 8. List disadvantag 1 es of 9. List the advantages of pas, 14. Define instances ang schemes, 15. What is data ind, 16. Explain functions of DBMS, cessing? Explain with suitable Ins of DBMS, Ping is implemented in thy early file processing s ystem, ependence, Explain its type, diagram and example.yen wy bavibutin i Seba by ave Mai 17, What fs meant by database model? Friis thelr types 1H Hxplain following models with exannpl, wvantanes wn Mad (i) Network model (i) Hierarchical Model (id) olational Model ISBTE Questions with Answers Summer 2022 ) Define data model, Jit Hs types in, Refer to Section 1,5, state types of databar Rofer to Section 1.1.5.2, Point (4), Explain advantages of DBMS over file processing systern Refer to Section 1.1.5. aa (Winter 2022) Deine we (ii) Instance. .. Refer to Sections 1.1.7 and 1.1.9.2, State any two advantages of DBMS. Refer to Section 1.1.5.3, |. Explain three level architecture of Database system. a abstraction Refer to Section 1.2.2 |. Draw the overall architecture of DBMS. Explain storage manager and components, Refer to Section 1.1.11 and Points (1) and Summer 2023 . Define the terms: ()) Database (ii) DBMS. Refer to Sections 1.2.2 and 1.1.3 List any four Codd’s rule, . Refer to Section 1.1.10, Winter 2023 Enlist any two Applications of DBMS. . Refer to Section 1.1.6, . Define; (H) Instance (ii) Schema, Refer to Sections 1.1.9. . State advantages of DBMS over file processing system. Refer to Section 1.1.5.3, Differentiate between network model and hierarchical model, (Any four points). S. Refer to Section 1.3,en 1.30 Introduction to Databagy Database Management System List disadvantages of typical file processing system Ans. Refer to Section 1.1.4, 2. Define: (i) Data Abstraction (ii) Data Redundancy, . Refer to Sections 1.1.7 and 1.1.5.1, Point (1). 3. Define: (i) Instance (ii) Schema. Ans. Refer to Section 1.1.9, Explain overall structure of DBMS. with the help of diagram. Ans. Refer to Section 1.1.11.