Terms: Data: Database: Database Management System: INTRODUCTION Data is defined as a collection of facts and figures that can be recorded and has implicit meaning. Database: Database is a collection of related data. Database Management System: DBMS is a collection of programs that enables users to create and maintain a database.

Properties of Database: A database represents some aspects of the real world. A database is a logically coherent collection of data with some inherent meaning. A random assortment of data cannot be termed as database. A database is designed, built and populated with data for a specific purpose. It has an intended group of users and preconceived applications in which these users are interested.

Types of Databases: Traditional Database: Textual or numeric in nature. Geographic Information System: Maps, weather data, satellite images. Multimedia Database: Pictures, video clips, sound messages. Data Warehouses and Online Analytical Processing: Integration of data and for decision making. Real Time and Active Database: Controlling industrial and manufacturing processes.

Database Applications: Banking: all transactions Airlines: reservations, schedules Universities: registration, grades Sales: customers, products, purchases Online retailers: order tracking, customized recommendations Manufacturing: production, inventory, orders, supply chain Human resources: employee records, salaries, tax deductions Databases touch all aspects of our lives.

Database Management System: DBMS consists of: Collection of interrelated data Set of programs to access the data The main goal is to provide an environment that is both convenient and efficient to use. DBMS provides for: Definition of structure for the storage of data. Provision of mechanisms for manipulating information. Safety of information in case of system crash or unauthorized access. Concurrency control in case of multi user environment.

DBMS facilitates for: Defining a database; Constructing a database; Manipulating a database.

Purpose of Database Systems: In the early days, database applications were built directly on top of file systems. What is a File System? In file system permanent records are stored in various files and different application programs are written to extract records from, and to add records to, the appropriate files.

2. Difficulty in accessing data: 3. Data isolation: Drawbacks of using file systems to store data: 1. Data redundancy and inconsistency: Multiple file formats, Programs in multiple programming languages, duplication of information in different files, data inconsistencies. 2. Difficulty in accessing data: Need to write a new program to carry out each new task 3. Data isolation: Data scattered in multiple files. multiple files and formats Difficult to write new application program to retrieve data. 4. Integrity problems: Consistency Constraints Integrity constraints (e.g. account balance >1000) become “buried” in program code rather than being stated explicitly Hard to add new constraints or change existing ones

5. Concurrent access by multiple users: 4. Atomicity of updates: Failures may leave database in an inconsistent state with partial updates carried out. Example: Transfer of funds from one account to another should either complete or not happen at all. Difficult to ensure this property in file system. 5. Concurrent access by multiple users: Concurrent access needed for performance. Uncontrolled concurrent accesses can lead to inconsistencies. Example: Two people reading a balance and updating it at the same time. 6. Security problems: Hard to provide user access to some, but not all, data Database systems offer solutions to all the above problems.

Main Characteristics of Database Technology: Self-contained nature of a database system: A DBMS catalog stores the description of the database. The description is called meta-data). This allows the DBMS software to work with different databases. Insulation between programs and data: This is called program-data independence. Allows changing data storage structures and operations without having to change the DBMS access programs.

3. Data Abstraction: A data model is used to hide storage details and present the users with a conceptual view of the database. 4. Support of multiple views of the data: Each user may see a different view of the database, which describes only the data of interest to that user. 5. Sharing of data: 6. Multi-user transaction Processing.:

Additional Benefits of Database Technology: Controlling redundancy in data storage. - Sharing of data among multiple users. - Restricting unauthorized access to data. - Providing multiple interfaces to different classes of users. - Representing complex relationships among data. - Enforcing integrity constraints on the database. - Providing backup and recovery services. - Potential for enforcing standards. - Flexibility to change data structures. - Reduced application development time. Availability of up-to-date information. Economies of scale.

Database Administrators: Users of Database: Database Administrators: authorizing access to database, Coordinating & monitoring database use, Acquiring software & hardware resources as needed, Accountable for breach of security or poor system response time. 2. Database Designers: Identify data to be stored in db, Select appropriate structure for storing data, Communicate with all users and understand their requirements, Design a database that meets user requirements.

3. End Users: Casual End Users: Occasionally access a db, Needs different information each time, Use sophisticated database query language. E.g. middle or high level managers. Naïve or Parametric End Users: Constantly query and update the database, E.g. Bank tellers, Railway reservation clerks etc. Sophisticated End Users: Users who use database to meet complex requirements. E.g. Engineers, scientists, business analysts. Stand alone Users: Use readymade program package to interact with database.

4. System Analyst & Application Programmers: System analyst determine the requirements of end users; Application programmers implement these specifications as programs. Both are called software engineers. 5. Operators & Maintenance Personnel: Responsible for the actual running and maintenance of H/W & S/W environment for the database system.