Chapter 1

Database System Architecture

Prepared By:
Ms. Ayushi Gondaliya
Assistant Prof.
SRCOE, RAJKOT
Outline
 Introduction to DBMS
 Application of DBMS
 Advantages of DBMS
 Basic terms of DBMS
 Three level architecture
 Data Abstraction
 Mapping and Data independence
 Database Users
 DBMS system Architecture
What is DBMS?
 Data
◦ Data is a collection of a distinct small unit of
information. It can be used in a variety of forms like
text, numbers, media, bytes, etc. it can be stored in
pieces of paper or electronic memory, etc.
◦ Ex: person name, age etc.

 Database
◦ Database is a collection of logically related data.
◦ A database is an organized collection of data, so that
it can be easily accessed and managed.
◦ Ex: university database, library, railway station
What is DBMS?
 Database Management System
◦ A database management system (DBMS)
refers to the technology for creating and
managing databases. DBMS is a software tool
to organize (create, retrieve, update, and
manage) data in a database.
◦ Ex: My SQL, Azure, Mongo DB, Oracal
Application Of DBMS
 Banking
 Airlines
 Universities
 Finance
 E-Commerce
 Manufacturing
 HR management
 Government Organization
Advantage Of DBMS
 Reducing Data Redundancy
 Sharing of Data
 Data Integrity
 Data Security
 Privacy
 Backup and Recovery
 Data Consistency
Basic terms of DB:
 Data:
◦ Data is nothing but facts and statistics stored or free flowing
over a network, generally it's raw and unprocessed.
◦ Ex: grade of students
 Information:
◦ Data becomes information when it is processed, organized
turning it into something meaningful.
◦ Ex: result of students(pass or fail)
 Metadata:
◦ Metadata is data about data.
◦ Ex: table name, column name etc..
Student
S_name S_rollno S_sem S_contactno
Xyz 123456 3 123456789
Continue..
 Data dictionary:
◦ A data dictionary is an information repository which contains
metadata.
 Data warehouse:
◦ A data warehouse is an information repository which stores data.
 Field:
◦ A field is a character or group of characters that have a specific
meaning.
◦ Ex: Xyz, 123456, 3, 123456789 is the field of Student table.
 Record/ tuple:
◦ A record is collection of logically related fields.
◦ Ex: collection of fields (s_name,s_rollno,s_sem,s_contactno)
forms a record of a student.
3 level ANSI/SPARC Database
System
 1. Internal Level
◦ The internal level has an internal schema
which describes the physical storage structure
of the database.
◦ The internal schema is also known as a
physical schema.
◦ It uses the physical data model. It is used to
define that how the data will be stored in a
block.
◦ The physical level is used to describe complex
low-level data structures in detail.
 2. Conceptual Level
◦ The conceptual schema describes the design of a
database at the conceptual level. Conceptual level
is also known as logical level.
◦ The conceptual schema describes the structure
of the whole database.
◦ The conceptual level describes what data are to
be stored in the database and also describes what
relationship exists among those data.
◦ In the conceptual level, internal details such as an
implementation of the data structure are hidden.
◦ Programmers and database administrators work
at this level.
 3. External Level
◦ At the external level, a database contains
several schemas that sometimes called as
subschema. The subschema is used to describe
the different view of the database.
◦ An external schema is also known as view
schema.
◦ Each view schema describes the database part
that a particular user group is interested and
hides the remaining database from that user
group.
◦ The view schema describes the end user
interaction with database systems.
Data abstraction:
 To made a easy communication of user
and database system, the developers hide
the internal irrelevant detail from the
users.
 Data Abstraction refers to the process of
hiding irrelevant details from the user.
mapping
 A mapping constraint is a data constraint that expresses
the number of entities to which another entity can be
related via a relationship set.
 It is most useful in describing the relationship sets that
involve more than two entity sets.
 For binary relationship set R on an entity set A and B,
there are four possible mapping cardinalities. These are
as follows:
◦ One to one (1:1)
◦ One to many (1:M)
◦ Many to one (M:1)
◦ Many to many (M:M)
Data independence
Data independence
 1. Physical Data Independence
◦ Physical data independence can be defined as the
capacity to change the internal schema without
having to change the conceptual schema.
◦ If we do any changes in the storage size of the
database system server, then the Conceptual
structure of the database will not be affected.
◦ Physical data independence is used to separate
conceptual levels from the internal levels.
◦ Physical data independence occurs at the logical
interface level.
Data independence
 2. Logical Data Independence
◦ Logical data independence refers characteristic of
being able to change the conceptual schema
without having to change the external schema.
◦ Logical data independence is used to separate the
external level from the conceptual view.
◦ If we do any changes in the conceptual view of
the data, then the user view of the data would
not be affected.
◦ Logical data independence occurs at the user
interface level.
Database Users
 Database Administrator (DBA)
 Naive users(End Users)
 Data Base Designers
 Application Programmer
 Sophisticated Users
 Casual Users / Temporary Users
Role of DBA
 Defining the Schema
 Defining Storage Structure and Access Method
 Defining Backup / Recovery Procedures
 Monitoring Performance
 Defining Security & Integrity Checks
 Liaising with Users
 Assistance to Application Programmers
DBMS System Architecture Or
Structure Of DBMS
DBMS System Architecture Or
Structure Of DBMS
 Database system can be divide into two
parts:
1) Query Processors Units
 DDL(data definition language) Interpreter
 DML(data manipulation language) compiler
 Embedded DML Pre-compiler
 Query evolution engine
2) Storage Manager Units
 Authorization Manager
 Integrity Manager
 File Manager
 Buffer Manager
Thank you