Database management system

DATABASE
MANAGEMENT SYSTEM
PRESENTED BY
SIMRAN KAUR

DATA
 Known facts that can be stored or
recorded is called data
 PERSISTENT DATA: It continues to exist
even, when the system is not active
 TRANSIENT DATA: it is created while an
application is running and not needed,
when the application has been
terminated.

DATABASE
 Database is a collection of related data
with a logically coherent structure with
some inherent meaning, some specific
purposes and for an intended group of
users and applications
 It is a physical organization of varying
complexity and size

BASIC CONCEPT OF DBMS
 Define the structure of a database
 Manage the storage of data, safely for long
periods of time, on some storage medium
controlled by DBMS
 Manipulate a database, with efficient user
interfaces to query the database
 Manage database usage for users with their
access rights, performance optimization,
sharing of data among several users, security
from accidents or unauthorized use
 Monitor and analyse database usage

KEY PEOPLE INVOLVED IN A DBMS
 DBMS IMPLEMENTER: Person who builds
system
 DATABASE DESIGNER: Person responsible
for preparing external schemas for
applications, identifying and integrating user
needs into a conceptual schema
 DATABASE APPLICATION DEVELOPER:
Person responsible for implementing
database application programs that facilitate
data access for end users

KEY PEOPLE INVOLVED IN A DBMS
 DATABASE ADMINISTRATOR: Person
responsible for defining the internal schema,
sub-schemas (with database designers) and
specifying mappings between schemas,
monitoring database usage and supervising
DBMS functionality
 CASUAL USERS AS END USERS:
Occasional unanticipated access to database
 PARAMETRIC USERS AS END USERS:
Users who query and update the database
through fixed programs

SCHEMA/INTENSION
 Schema comprises the definition of
domains for data elements (attributes)
and the specification of constraints, to
define the data structure part of the
schema
 Intension is a constant value that gives
the name, structure of table and the
constraints laid on it
 Schemas don’t change frequently

INSTANCE/EXTENSION
 Databases change over time because
records are inserted and deleted
frequently
 The collection of information stored in the
database at a particular moment is called
an instance of the database while
extension means the number of tuples
present in a table at any instance
 This is dependent on time

DATA ABSTRACTION
 Hiding the complexity from users through
several levels of abstraction, to simplify
users’ interactions with the system, as
many database systems users are not
computer trained
 Three levels of data abstraction:
i) Physical level
ii) Logical level
iii) View level

PHYSICAL LEVEL
 Physical level is the lowest level of
abstraction and describes how the data
are actually stored and complex low level
data structures in detail
 At the physical level, an employee record
can be described as a block of consecutive
storage locations

LOGICAL LEVEL
 Logical level is the next higher level of
abstraction and describes what data are
stored and what relationships exist among
those data
 At logical level, each such record is
described by a type definition and the
interrelationship of these record types is
defined as well
 Database administrators usually work at
this level of abstraction

VIEW LEVEL
 View level is the highest level of
abstraction and describes only part of the
entire database and hides the details of
the logical level
 At this level, several views of the
database are defined and database users
see these views
 The views also provide a security
mechanism to prevent users from
accessing certain parts of the database

FUNCTIONALITY OF DBMS
 Concurrency control
 Backup and recovery
 Redundancy management
 Access control
 Performance optimisation
 Metadata management
 Active features (rules, triggers)

CONCURRENCY CONTROL
 It is responsible for ensuring correctness
of competing accesses to same data
 One or more Structure Query Language
(SQL) statements altogether treated as
one single unit
 Correctness of data requires four
desirable properties (ACID properties)

BACKUP AND RECOVERY
 Facilities for recovering from hardware
and software failures
 If the computer system fails during a
complex update program, the database
must be restored to its state before the
program started, or the program must be
resumed, where it was interrupted so that
its full effect is recorded in database
 In a multiuser environment, it is more
complex and important

REDUNDANCY MANAGEMENT
 Redundancy means storing several copies of
the same data
 Redundant entries are frequent in traditional
file processing; a goal of the database
approach was to control redundancy as much
as possible
 Problems with redundancy includes wastage
of storage space, duplication of effort to
perform a single conceptual update, danger
of introducing inconsistency, if multiple
updates are not coordinated

ACCESS CONTROL
 Responsible for enforcing security and
authorisation (e.g., who can create new
bank accounts) and data (e.g., which
bank accounts one can see)
 It is all about who accesses what data, to
do what, when, from where, etc

PERFORMANCE OPTIMIZATION
 Performing physical reorganizations to
enhance performance, e.g., adding index,
dropping index, sorting file
 Performance optimization is made
possible by physical data independence
and high level data models with user
programs which can be optimized through
DBMS software

METADATA MANAGEMENT
 Metadata means data about data
 It involves storing of information about
other information
 With different types of media being used,
references to the location of the data can
allow management of diverse repositories

ACTIVE FEATURES
 Data objects, database statistics, physical
structures and access paths, user access
privileges, etc, are active features of
DBMS

Database management system

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Database management system