Database System Concepts and Architecture

Question 1

A collection of concepts that can be used to describe the structure of the database.

Answer 1

Data Model

Question 2

Categories of Data Model

Answer 2

1. Conceptual (or High-level) Data Models
2. Representational (or Implementation) Data Models
3. Physical (or Low-level) Data Models

Question 3

Provide concepts that are close to the way many users perceive data

Use concepts such as entities, attributes, and relationships

Answer 3

Conceptual Data Models

Question 4

Provide concepts that may be easily understood by end users but are not too far removed from the way data is organized in computer storage

Used most frequently in traditional commercial DBMSs

Include relational, network, and hierarchical data models

Answer 4

Representational Data Models

Question 5

Representational Data Models are also known as __________________ since they represent data by using record structures

Answer 5

record-based data models

Question 6

Provide concepts that describe the details of how data is stored on the computer storage media

Describe how data is stored as files in the computer by representing information such as record formats, record orderings, and access paths

Answer 6

Physical Data Models

Question 7

Description of the database

Answer 7

Schema (or Database Schema)

Question 8

Specified during database design and is not expected to change frequently

Answer 8

Schema

Question 9

When schema changes, it is called?

Answer 9

Schema Evolution

Question 10

a displayed schema

Answer 10

Schema Diagram

Question 11

Description of the schema constructs and constraints

Stored in database catalog (or database dictionary)

Answer 11

Meta-data

Question 12

Data in the database at a particular moment in time

Answer 12

Database State

Question 13

Database State is also called as

Answer 13

database snapshot, current set of occurrences / instances

Question 14

When database is defined (schema specified) but no data

Answer 14

Empty State

Question 15

When database is first loaded / populated with data

Answer 15

Initial State

Question 16

Database state NOW

Answer 16

Current State

Question 17

State that satisfies the structure and constraints specified in the
schema; DBMS must ensure this

Answer 17

Valid State

Question 18

Three-Schema Architecture

Answer 18

External level
Conceptual Level
Internal Level

Question 19

Describes the physical storage structure of the database

Uses physical data model

Answer 19

Internal Schema

Question 20

Helps visualize and achieve the database system approach’s characteristics of having a self-describing nature, data independent and capable of multiple user views.

Answer 20

Three-Schema Architecture

Question 21

Describes the structure of the whole database for a community of users

Typically uses representational data model to describe it

Answer 21

Conceptual Schema

Question 22

Describes the part of the database that a particular user group is interested in

Typically uses representational data model to describe it

Answer 22

User View (or External Schema)

Question 23

Process of transforming requests and results between levels

Answer 23

Mapping

Question 24

Capacity to change the schema at one level of a database system without having to change the schema at the next higher level

Answer 24

Data Independence

Question 25

Two types of Data Independence

Answer 25

Logical and Physical

Question 26

Capacity to change the conceptual schema without having to change external schemas or application programs

Answer 26

Logical Data Independence

Question 27

Capacity to change the internal schema without having to change the conceptual schema

Answer 27

Physical Data Independence

Question 28

Language used by DBAs and Database Designers to define (and/or modify) the description of the database

Answer 28

Data Definition Language (DDL)

Question 29

Language (or set of operations) used by database users to manipulate the database (i.e., retrieval, insertion, deletion, modification)

Answer 29

Data Manipulation Language (DML)

Question 30

Specifies database access control which grant or revoke privilege to or from users

Answer 30

Data Control Language (DCL)

Question 31

Language that allows database users to manipulate processing of transactions

Answer 31

Transaction Control Language (TCL)

Question 32

DBMS Languages

Answer 32

Data Definition Language (DDL) Data Manipulation Language (DML) Data Control Language (DCL) Transaction Control Language (TCL)

Question 33

DBMS Interfaces

Answer 33

* Command-line Interface * Menu-based interfaces for Web Clients or Browsing * Apps for Mobile Devices * Forms-based Interfaces * Graphical User Interfaces * Natural Language Interfaces * Keyword-based Database Search * Speech Input and Output * Interfaces for Parametric Users * Interfaces for DBAs

Question 34

Processes schema definitions specified in the DDL and stores/updates the meta-data in the database system catalog.

Answer 34

DDL Compiler

Question 35

Includes information such as names/data types of data items, storage details of files, constraints as well as information needed by other modules

Answer 35

Database System Catalog (Data Dictionary)

Question 36

Parses and validates queries for correctness of syntax and file/data element names Compiles queries into internal form

Answer 36

Query Compiler

Question 37

Concerned with rearrangement/reorder of operation, elimination of redundancies, and use of efficient search algorithms prior to execution

Answer 37

Query Optimizer

Question 38

Consults the DB system catalog then generate executable code that performs the necessary operation(s) in an optimal way

Answer 38

Query Optimizer

Question 39

Extracts DML commands from application programs

Answer 39

Precompiler

Question 40

Compiles extracted DML commands into object code which will later be linked with the rest and turned into compiled transaction(s)

Answer 40

DML Compiler

Question 41

Executes privileged commands, executable query plans, and compiled transactions

Answer 41

Runtime Database Processor

Question 42

Refers to DB system catalog and may update statistics

Answer 42

Runtime Database Processor

Question 43

Works with Stored Data Manager and performs other tasks such as buffer management

Answer 43

Runtime Database Processor

Question 44

Controls access to DBMS information stored on disk

Answer 44

Stored Data Manager

Question 45

Uses basic operating system services for carrying low-level input/output (read/write) operations between disk and memory

Answer 45

Stored Data Manager

Question 46

Subsystems working with the Runtime Database Processor for the purpose of transaction management

Answer 46

Concurrency Control and Backup & Recovery

Question 47

Database System Utilities

Answer 47

Loading Backup Database storage reorganization Performance monitoring

Question 48

Add data (in bulk) into the database; Maybe from files or from another database

Answer 48

Loading

Question 49

Create backup copy (or copies) of database onto mass storage medium (tape, slower/cheaper disk); Capability to do incremental backups

Answer 49

Backup

Question 50

Reorganize database files into different file organizations and/or create new access paths to improve performance

Answer 50

Database storage reorganization

Question 51

Monitors DB usage and provide statistics to the DBA; Helps in making decisions on whether changes are needed to improve performance

Answer 51

Performance Monitoring

Question 52

Database Application Architecture developed to deal with computing environments with large number of devices and/or software connected via a network

Answer 52

Centralized (Client-/server)

Question 53

Two-Tier vs Three-Tier Client/Server

Answer 53

**Two-Tier** are much used in earlier generations and the *application resides at the client machine*, where as **Three-tier** is used in modern database applications, where the *client machine is merely for frontend* and does not contain any direct database calls. Front end communicates with application server where business logic is embedded (instead of multiple clients)

Question 54

Classification of DBMS (Based on Data Model)

Answer 54

* Relational * Object * NO SQL/Big Data Systems * Document-Based * Graph-Based * Column-Based * Key-Value * XML * Legacy * Hierarchical * Network

Question 55

Classification of DBMS (Based on Number of Users)

Answer 55

**Single-user:** Supports only one user at a time; Mostly used with PCs **Multiuser:** Supports concurrent multiple users; Majority of DBMSs are in this classification

Question 56

Classification of DBMS (Based on Number of Sites)

Answer 56

**Centralized:** Data is stored at a single computer site **Distributed:** Database and DBMS distributed over many sites connected by a computer network

Question 57

Two Types of Distributed DBMS

Answer 57

**Homogeneous DDBMS:** Use the same DBMS software at all sites **Heterogeneous DDBMS**: Can use different DBMS software at each site

Question 58

Classification of DBMS (Based on Cost)

Answer 58

* **Open-Source (Free):** Supported by third-party vendors with additional services * **Paid:** Different kinds of licensing scheme