(Aktu Btech) Database Management System Important Unit-1 Introduction

With Aktu’s Quantum Notes for Database Management System, you can improve your B.Tech studies. With the help of these crucial, repeating questions and notes, you may master vital topics and do well on exams. Unit-1 Introduction

Dudes 🤔.. You want more useful details regarding this subject. Please keep in mind this as well.

Important Questions For Database Management System:
*Quantum               *B.tech-Syllabus
*Circulars                *B.tech AKTU RESULT
* Btech 3rd Year    * Aktu Solved Question Paper

Q1. What is database management system (DBMS) ? What are the tasks performed by users in DBMS?

Ans.

• 1. Database management system (DBMS) is a software which is use to manage the database. For example, MySQL, Oracle, are commercial database which is used in different applications. 
• 2. DBMS provides an interface to perform various operations like database creation, storing data, updating data, creating a table in the database etc. 
• 3. It provides protection and security to the database. In case of multiple users, it also maintains data consistency.

DBMS allows users the following tasks: 

• 1. Data definition: It is used for creation, modification, and removal of database objects that defines the organization of data in the database. 
• 2. Data updation: It is used for the insertion, modification, and deletion of the actual data in the database. 
• 3. Data retrieval: It is used to retrieve the data from the database which can be used by applications for various purposes. 
• 4. User administration: It is used for registering and monitoring users, maintaining data integrity, enforcing data security, dealing with concurrency control, monitoring performance and recovering information corrupted by unexpected failure.  

Q2. Discuss the role of database administrator.  

Ans. Database administrators are the personnel’s who has control over data and programs used for accessing the data. 

Functions/role of database administrator (DBA): 

• 1. Schema definition: 
  • a. Original database schema is defined by DBA. 
  • b. This is accomplished by writing a set of definitions, which are translated by the DDL compiler to a set of labels that are permanently stored in the data dictionary.
• 2. Storage structure and access method definition: 
  • a. The creation of appropriate storage structure and access method. 
  • b. This is accomplished by writing a set of definitions, which are translated by the data storage and definition language compiler. 
• 3. Schema and physical organization and modification: 
  • a Modification of the database schema or the description of the physical storage organization. 
  • b. These changes are accomplished by writing a set of definition to do modification to the appropriate internal system tables. 
• 4. Granting of authorization for data access: DBA grants different types of authorization for data access to the various users of the database. 
• 5. Integrity constraint specification: DBA carry out data administration in data dictionary such as defining constraints.

Q3. Draw the overall structure of DBMS and explain its components in brief.

Ans. A database system is partitioned into modules that deal with each of the responsibilities of the overall system. The functional components of a database system can be broadly divided into two components: 

1. Storage Manager (SM): A storage manager is a program module that provides the interface between the low level data stored in the database and the application programs and queries submitted to the system. The SM components include: 

• a. Authorization and integrity manager: It tests for the satisfaction of integrity constraints and checks the authority of users to access data. 
• b. Transaction manager: It ensures that the database remains in a consistent state despite of system failures and that concurrent transaction executions proceed without conflicting. 
• c. File manager: It manages the allocation of space on disk storage and the data structures are used to represent information stored on disk. 
• d. Buffer manager: It is responsible for fetching data from disk storage into main memory and deciding what data to cache in main memory. The buffer manager is a critical part of the database system, since it enables the database to handle data sizes that are much larger than the size of main memory. 

2. Query Processor (QP): The Query Processor (Query Optimizer) is responsible for taking every statement sent to SQL Server and figure out how to get the requested data or perform the requested operation. The QP components are : 

• a. DDL interpreter: It interprets DDL statements and records the definition in data dictionary. 
• b. DML compiler: It translates DML statements in a query language into an evaluation plan consisting of low-level instructions that the query evaluation engine understands. 
• c. Query optimization: It picks the lowest cost evaluation plan from among the alternatives. 
• d. Query evaluation engine: It executes low-level instructions generated by the DML compiler.

Q4. What are data models ? Briefly explain different types of data models. 

Ans. Data models: 

• 1. Data models define how the logical structure of the database is modeled. 
• 2. Data models are a collection of conceptual tools for describing data, data relationships, data semantics and consistency constraints. 
• 3. Data models define how data is connected to each other and how they are processed and stored inside the system.

Types of data models: 

1. Entity relationship model: 

• a. The entity relationship (ER) model consists of a collection of basic objects, called entities and of relationships among these entities 
• b. Entities are represented by means of their properties, called attributes. 

2. Relational model: 

• a. The relational model represents data and relationships among data by a collection of tables, each of which has a number of columns with unique names.
• b. Relational data model is used for data storage and processing.
• c. This model is simple and it has all the properties and capabilities required to process data with storage efficiency. 

3. Hierarchical model: 

• a. In hierarchical model data elements are linked as an inverted tree structure (root at the top with branches formed below). 
• b. Below the single root data element are subordinate elements each of which in turn has its own subordinate elements and so on, the tree can grow to multiple levels. 
• c. Data element has parent child relationship as in a tree. 

4. Network model: 

• a. This model is the extension of hierarchical data model. 
• b. In this model there exist a parent child relationship but a child data element can have more than one parent element or no parent at all. 

5. Object-oriented model: 

• a. Object-oriented models were introduced to overcome the shortcomings of conventional models like relational, hierarchical and network model. 
• b. An object-oriented database is collection of objects whose behaviour, state, and relationships are defined in accordance with object oriented concepts (such as objects, class, etc.).

Q5. Describe data schema and instances.

Ans.

• 1. The description of a database is called the database schema, which specified during database design and is not expected to change frequently. 
• 2. Most of the data models have certain convention for displaying schema as diagram which is called schema diagram. 
• 3. A schema diagram displays only some aspects of a schema, such as the names of record types and data items, and some types of constraints.  

For example: Schema diagram for student info database

Student (Name, Student number, Class, Branch) 

Course (Course_name, Course_number, Department)

Instances: 

• 1. The data in the database at a particular moment is called a database state or snapshot. It is also called the current set of occurrences or instances in the database.
• 2. In a database state, each schema construct has its own current set of instances. 
• 3. Many database states can be constructed to correspond to a particular database schema. Every time we insert or delete a record or change the value of a data item in a record, we change one state of the database into another state.  

Q6. Explain data independence with its types.  

Ans. Data independence: Data independence is defined as the capacity to change the schema at one level of a database system without having to change the schema at the next higher level. 

Types of data independence : 

• 1. Physical data independence: 
  • a. Physical data independence is the ability to modify internal schema without changing the conceptual schema. 
  • b. Modification at the physical level is occasionally necessary in order to improve performance.
  • c. It refers to the immunity of the conceptual schema to change in the internal schema. 
  • d. Examples of physical data independence are reorganizations of files, adding a new access path or modifying indexes, etc. 
• 2. Logical data independence: 
  • a. Logical data independence is the ability to modify the conceptual schema without having to change the external schemas or application programs.
  • b. It refers to the immunity of the external model to changes in the conceptual model. 
  • c. Examples of logical data independence are addition/removal of entities.

Database Management System Btech Quantum PDF, Syllabus, Important Questions

Database Management System Quantum PDF | AKTU Quantum PDF:

AKTU Important Links | Btech Syllabus

Important Links-Btech (AKTU)