Database System Concepts AND architecture [Autosaved].pptx

Database System Concepts
AND architecture

Data Model:
 A data model is a collection of concepts that can be
used to describe the structure of a database.
 By structure of a database we mean the data
types, relationships and constraints that apply to
the data.
 It defines the data elements and the relationships
between the data elements.
 Data Models are used to show how data is stored,
connected, accessed and updated in the database
management system.
 Though there are many data models being used
nowadays but the Relational model is the most
widely used model.

High-level or conceptual data models :
 high level or conceptual model is the User level data model .
 This provides concepts that are close to the way that many
users perceive data.
 Conceptual data models use concepts such as entities,
attributes, and relationships.
 Entity: Represents a real world object such as Student,
Employee.
 Attribute: Represents property of interest that describes an
entity, such as name or Salary
 Relationships: Relationships among two or more entities.
Low level-Physical data models:
 provides concepts that describe the details of how data is
stored in the computer model.
 Low level data model is only for Computer specialists not for
end-user.
Representation data model:
 provide concepts that describe the details of how data is
stored on the computer storage media, typically magnetic
disks.
 Physical data models describe how data is stored as files in
the computer by representing information such as record

Types of Data Models :
1. Hierarchical Model
2. Network Model
3. Relational Model
4. Object-oriented Data Models
5. Object-Relational Models
Hierarchical Model:
1. Hierarchical Model was the first DBMS model. This
model organizes the data in the hierarchical tree
structure.
2. The hierarchy starts from the root which has root
data and then it expands in the form of a tree
adding child node to the parent node.

 The data here is organized in a tree-like structure
where the one-to many relationship is between the
data types.
 Also, there can be only one path from parent to any
node.
 Each child node has a parent node but a parent node
can have more than one child node.
 Multiple parents are not allowed.
 If a parent node is deleted then the child node is
automatically deleted.
 Pointers are used to link the parent node with the
child node and are used to navigate between the
stored data.

Advantages:
 Any change in the parent node is automatically
reflected in the child node so, the integrity of data is
maintained
Disadvantages:
 Complex relationships are not supported.

Network Model :
 This model is an extension of the hierarchical model.
 It was the most popular model before the relational
model.
 This model is the same as the hierarchical model,
the only difference is that a record can have more
than one parent.
 It replaces the hierarchical tree with a graph.
 In this model, as there are more relationships so
data is more related.
 This model has the ability to manage one-to-one
relationships as well as many-to many relationships.
 As there are more relationships so there can be
more than one path to the same record.

 The operations on the network model are done with
the help of the circular linked list.
 The current position is maintained with the help of a
program and this position navigates through the
records according to the relationship.
Advantages of Network Model :
 The data can be accessed faster as compared to the
hierarchical model.
 Network model and there can be more than one path
to reach a particular node.
Disadvantages of Network Model :
 As more and more relationships need to be handled
the system might get complex.

Database System Concepts AND architecture [Autosaved].pptx

Relational Model :
 Relational Model is the most widely used model.
 In this model, the data is maintained in the form of a
two-dimensional table.
 All the information is stored in the form of row and
columns.
 The basic structure of a relational model is tables.
 So, the tables are also called relations in the
relational model.
 Each row in the table is called tuple.
 A row contains all the information about any
instance of the object.

 Attribute or field: Attributes are the property which
defines the table or relation.
 In the above example, we have different attributes of
the employee like Salary, Mobile_no, etc.

Advantages of Relational Model :
 Simple: This model is more simple as compared to
the network and hierarchical model.
Disadvantages of Relational Model :
 Hardware Overheads: For hiding the complexities
and making things easier for the user this model
requires more powerful hardware computers and
data storage devices.

Object-oriented Data Model :
 The real-world problems are more closely
represented through the object-oriented data
model.
 In this model, both the data and relationship are
present in a single structure known as an object.
 We can store audio, video, images, etc in the
database which was not possible in the relational
model.
 In this model, two are more objects are connected
through links.
 We use this link to relate one object to other
objects.
 This can be understood by the example given

Object-oriented Data Model consist of the
following object oriented Concepts:
1.Object: The real world entities and situations are
represented as objects in the object oriented
database model.
2. Attributes and Methods: Every object has certain
characteristics .They are represented using
attributes.
3.Class: Similar attributes and methods are grouped
together using a class. An object can be called
Instance of the class.
4. Inheritance: A new class can be derived from the
original class.

 the above example, we have two objects Employee
and Department.
 All the data and relationships of each object are
contained as a single unit.
 The attributes like Name, Job_title of the employee
and the methods which will be performed by that
object are stored as a single object.
 The two objects are connected through a common
attribute i.e the Department_id and the
communication between these two will be done with
the help of this common id.
 The Behaviour of the objects is represented using
methods.
 Similar attributes and methods are grouped together

Object-Relational Models :
 An Object relational model is a combination of a
Object oriented database model and a Relational
database model.
 So, it supports objects, classes, inheritance etc. just
like Object Oriented models and has support for
data types, tabular structures etc. like Relational
data model.
 One of the major goals of Object relational data
model is to close the gap between relational
databases and the object oriented practices
frequently used in many programming languages
such as C++, C#, Java etc.
The advantages of the Object Relational model are
−

Complex Data Types
 Complex data types can be formed using existing
data types
Extensibility
 The functionality of the system can be extended in
Object relational data model.
Disadvantages of Object Relational model
 The object relational data model can get quite
complicated and difficult to handle at times as it is a
combination of the Object oriented data model and
Relational data model and utilizes the functionalities
of both of them.

Schema and Instances:
Database Schema: A database schema represents the
logical view of the entire database.
 It defines how the data is organized and how the
relations among them are associated.
 Schemas provide a logical classification of objects in the
database.
 A schema can contain tables, views, triggers, functions,
packages, and other objects.
 A database schema defines its entities and the
relationship among them.
 It contains a descriptive detail of the database, which
can be depicted by means of schema diagrams.
 It’s the database designers who design the schema to
help programmers understand the database and make it
useful.

 From the above schema diagram student and Grade
report are related and course and prerequisite and
section are related.
DBMS Instance :
 The data stored in database at a particular moment of
time is called instance of database.
 Database State: Refers to the content of a database
at a moment in time.
 Initial Database State: Refers to the database state
when it is initially loaded into the system.
 Valid State: A state that satisfies the structure and
constraints of the database.

SIMPLIFIED DATABASE SYSTEM :
 A database system is Computer-Based system to
record and maintain the information. A Database
Management System consists of a collection of
inter-related data and a set of program to access
those data.
 The database and the DBMS software together is a
Database system.
 It consists of the following
1. User/Programmers
2. Applications programs/Queries
3. Software to process Queries/programs
4. Software to Access stored data
5. DBMS Catalog Contains the Stored database
definition (Metadata)
6. The Physical Stored database

A Simplified Database System
Environment

 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
 The collection of data, usually referred to as the
database, contains information about one particular
enterprise.
 The primary goal of DBMS is to provide an environment
that is both convenient and efficient to use in retrieving
and storing database information
 This system involves the control of how databases are
Created, interrogated and maintained to provide
information needed by end users and the organization.
 DBMS acts as the interface between the application
programs and database.
 There are many different types of DBMS, ranging from
small systems that run on personal computers to huge
systems that run on mainframes.
 Ex: Computerized library system

DBMS Architecture :
 Every database system logically organizes data with
respect to some model is called Data model. A Data
model describes how various pieces of data in the
database are logically related to each other
 The data model represents the relationship between
entities. The database model is also well known as
Database Architecture.
 The structure of a DBMS may be analyzed in two
separate architectures
 Logical DBMS Architecture
 Physical DBMS Architecture.

Logical DBMS Architecture (Three Schema/Level
DBMS Architecture):
 The three schema architecture is also called
ANSI/SPARC architecture or three-level architecture.
 The logical Architecture describes how data in the
database is perceived by users.
 It is now concerned with how the data is handled and
processed by the DBMS, but only with how it looks.
 The goal of the Three-schema architecture is to separate
the user application from the physical database.
 In this architecture, schemas can be defined at the
following three levels
 There are following three levels or layers of DBMS
Architecture
 External Level
 Conceptual Level
 Internal Level

Physical level (or Internal View / Schema): The lowest
level of abstraction describes how the data are actually
stored.
 The physical level describes physical storage structure of
the database.
 Essentially, the physical schema summarizes how the
relations described in the conceptual schema are actually
stored on secondary storage devices such as disks and
tapes.
Logical level (or Conceptual View / Schema): The next-
higher level of abstraction describes what data are stored
in the database, and what relationships exist among
those data.
 The logical level thus describes the entire database in
terms of a small number of relatively simple structures.
 It hides physical storage details, concentrating upon
describing entities, data types, relationships, user
operations, and constraints.

View level (or External View / Schema): The highest
level of abstraction Describes the various user views..
 It describes the part of the database that a particular
user group is interested in and hides the rest of the
database from that user group.
 Usually a high-level model is used here.
Mapping:
 The processes of transforming requests and results
between levels are called mappings.
 In a DBMS based on the three-schema architecture,
each user group refers to its own external schema.
 Hence, the DBMS must transform a request specified on
an external schema into a request against the
conceptual schema, and then into a request on the
internal schema for processing over the stored
database.
 If the request is a database retrieval, the data extracted

 There are basically two types of mapping in the
database architecture:
◦ External/conceptual mapping
◦ Conceptual/ internal mapping
Conceptual/ Internal Mapping
 The Conceptual/ Internal Mapping lies between the
conceptual level and the internal level. Its role is to
define the correspondence between the records and
fields of the conceptual level and files and data
structures of the internal level.
External/ Conceptual Mapping
 The external/Conceptual Mapping lies between the
external level and the Conceptual level. Its role is to
define the correspondence between a particular
external and the conceptual view.

Physical DBMS Architecture
The physical Architecture describes the software components used to
enter and process data, and how these software components are
related and interconnected.
The physical DBMS Architecture divided into 2 parts:
 Back end
 Front end
Back end:
 The back end is responsible for managing the physical database and
providing necessary support and mappings for the internal, conceptual
levels.
 Other benefits of DBMS, such as Security, integrity and access
control are also responsibility of the back end
Front end:
 The Front end is really an application that runs on the top of the
DBMS. These may be applications provided by the DBMS vendor,
the use of the third party.
 The user interact with the front end and may not even be aware that

DATA – INDEPENDENCE
 Data Independence is defined as a property of DBMS that
helps you to change Database Schema at one level of a
database system without requiring to change the Schema
at the next higher level.
 Data Independence is one of the main advantages of
DBMS
 The ability to modify a schema definition in one level
without affecting Schema definition in the next higher
level is called “Data Independence”
 There are two kinds of Data Independence
 1. Physical Data Independence
 2. Logical Data Independence

Database Languages:
 Database Languages: A DBMS has appropriate
languages and interfaces to express database
queries and updates.
 Database languages can be used to read, store and
update the data in the database.
Types of Database Language:

1. Data Definition Language :
 DDL stands for Data Definition Language. It is used
to define database structure or pattern.
 It is used to create schema, tables, indexes,
constraints, etc. in the database.
 Data definition language is used to store the
information of metadata like the number of tables
and schemas, their names, indexes, columns in
each table, constraints, etc.
 The data definition language (DDL) is used by the
DBA and by database designers to define both
schemas when no strict separation of levels is
maintained .
 The DBMS will have a DDL compiler whose function
is to process DDL statements in order to identify
descriptions of the schema constructs and to store

Storage Definition Language (SDL):
 The storage definition language (SDL), is used to specify
the internal schema. The mappings between the two
schemas may be specified in either one.
 View Definition Language (VDL), View definition
language is used to specify user views and their
mappings to the conceptual schema.
Here are some tasks that come under DDL:
 Create: It is used to create objects in the database.
 Alter: It is used to alter the structure of the database.
 Drop: It is used to delete objects from the database.
 Truncate: It is used to remove all records from a table.
 Rename: It is used to rename an object.
 Comment: It is used to comment on the data dictionary.
These commands are used to update the database
schema that's why they come under Data definition

2. Data Manipulation Language :
 DML stands for Data Manipulation Language.
 It is used for accessing and manipulating data in a
database.
 Data manipulation languages (DML) are used to perform
manipulation operation such as retrieval, insertion,
deletion, and modification of the data.
Here are some tasks that come under DML:
 Select: It is used to retrieve data from a database.
 Insert: It is used to insert data into a table.
 Update: It is used to update existing data within a table.
 Delete: It is used to delete all records from a table.
 Merge: It performs UPSERT operation, i.e., insert or
update operations.
 Call: It is used to call a structured query language or a
Java subprogram.
 Explain Plan: It has the parameter of explaining data.
 Lock Table: It controls concurrency.

3. Data Control Language :
 DCL stands for Data Control Language.
 It is used to retrieve the stored or saved data.
 The DCL execution is transactional.
 It also has rollback parameters. (But in Oracle
database, the execution of data control language
does not have the feature of rolling back.)
Here are some tasks that come under DCL:
 Grant: It is used to give user access privileges to a
database. Grant to allow specified users to perform
specified tasks.
 Revoke: It is used to take back permissions from
the user.
There are the following operations which have the

4. Transaction Control Language :
 TCL is used to run the changes made by the DML
statement.
 TCL can be grouped into a logical transaction.
Here are some tasks that come under TCL:
 Commit: It is used to save the transaction on the
database.
 Rollback: It is used to restore the database to
original since the last Commit.

DBMS Interfaces
Interfaces are the programs which convert system
language to user understandable language and user
language to system understandable language. So its work
likes a translator which provides an environment in which
a user can easily operate the system
Types of interfaces provided by the DBMS include
 Menu-Based interface for web clients or browsing
 Forms-based interfaces
 GUI’s
 Natural Language interfaces
 Interfaces for parametric users
 Interfaces for the DBA

 Menu-Based interface for web clients or browsing:
These interfaces are used by the stand-alone users. These
interfaces present a set of options called menu to the users,
from which user can select an option
 Forms-based Interfaces: These are used by the parametric
users. In this type a form is displayed to the user. User has to
fill all the information required through form fields
 Graphical user Interfaces (GUI’s): these are used by both
user, by parametric and by stand alone user. Both Form based
and Menu based is called GUI. Displays a schema to the user in
diagram form. The user can select his/her options using a
mouse pointer.
 Natural language Interfaces: these Interfaces are used by the
Sophisticated users. This includes commands in English and it
will have its own Schema
 Interfaces for Parametric users: parametric users have small
set of operations they perform. Analyst and programmers
design and implement a special interface for each class of naive
users
 Interfaces for the DBA: Systems contain privileged

Database System Environment
The term database system refers to an organisation of
components that define and regulate the collection,
management, and use of data within a database
In high level view the database system is composed of
following five major components:
 Hardware Components in a database System
 Software Components in a database System
 People in a Database System Environment
 Procedure in a Database Environment
 Data in the Database
1. Hardware Components in a database System
Environment
Hardware identifies all the system’s physical devices. It
includes computers, computer peripherals, network

Database System Concepts AND architecture [Autosaved].pptx

More Related Content

What's hot (20)

Similar to Database System Concepts AND architecture [Autosaved].pptx (20)

More from Koteswari Kasireddy (20)

Recently uploaded (20)

Database System Concepts AND architecture [Autosaved].pptx