This document discusses distributed database systems. It defines centralized, distributed, and decentralized database systems. The key topics covered include distributed database management systems (DDBMS), advantages and disadvantages of DDBMS, distributed database design involving data fragmentation, replication and allocation, functions of a DDBMS, types of DDBMS including homogeneous and heterogeneous, and database transparency and gateways. The document is presented by a group with members Zupash, Sana, Marhaba and a group leader Hira Anwar.

2. BrAinY 4
Presented to:-
Ma’am Asima Jamil & Class
GROUP MEMBERS
Zupash
Sana
Marhaba
GROUP LEADER
Hira Anwar

3. DISTRIBUTED
DATABASES
OUR TOPIC OF PRESENTATION IS

4. Topics to be discussed are
 Centralized database system
 Distributed database
 Decentralized database
 Distributed DBMS
 Advantages and disadvantages of DDBMS
 Distributed database design
 Function of DDBMS
 Types of DDBMS
 DBMS transparency & gateways

5.  Centralized DB system
 Distributed DB system
 Decentralized DB system
 Distributed DBMS
Presented by
ZUPASH KIRAMAT

6. Centralized Database system
A centralized database
sometimes abbreviated
CDB) is a database that
is located, stored, and
maintained in a single
location.This location is
most often a central
computer or database
system, for example a
desktop or server CPU, or
a mainframe computer

7. Distributed DB system
 database In a Distributed Database System
the database is stored/spread physically
across computers or sites in different
locations that are connected together by
some form of data communication network.

8. Distributed DB system

9. Difference

10. Decentralized DB system
Database is
stored on
computers or
sites on
different
location but the
computers are
not
interconnected
via a network.

11. Distributed DBMS
 A DDBMS is a centralized application that manages a
distributed database as if it were all stored on the same
computer.
 Synchronizes all the data periodically, and in cases
where multiple users must access the same data.

12. ADVANTAGES AND
DISADVANTAGES
SANA AYUB

13. ADVANTAGES
 Local control
 Reliability and availability
 Efficient querying process
 Modular growth
 Economics

14. Advantages…

15. Disadvantages
 Software complexity and high costs
 Processing overheads
 Data integrity
 Complex DB design
 Slow response

16. DISTRIBUTED DB DESIGN
HIRA ANWAR

17. Distributed DB design
Three additional factors are involved
1.Data Fragmentation
2.Data replication
3.Data allocation

18. Distributed Database Design
 Fragmentation
 Relation may be divided into a number of sub-relations,
which are then distributed.
 Allocation
 Each fragment has to be allocated to one or more sites.
 Replication
 Copy of fragment may be maintained at several sites.

19. Fragmentation
 The DB may be broken into logical units.
Types
 Horizontal fragmentation
• table broken into two or more set of rows.
 Vertical fragmentation
• table broken into two or more set of columns

20. 41
Horizontal and Vertical
Fragmentation

21. Data replication
 A copy of each fragment may be stored at
several sites.
 Data replication is the design process of
deciding which fragment will be replicated.

22. Data Allocation
 Each fragment have to be allocated to
one or more sites, where it will be
stored.
 Three strategies used for this purpose:
1. Fragmented data allocation.
2. Complete replication
3. Selective replication

23. Fragmented data allocation.
 Database partitioned into disjoint fragments, each
fragment assigned to one site.
 Also called non-redundant allocation or
partitioned allocation.
Advantages:
1. Efficiency
2. Security
Disadvantages
1. Inconsistent access speeds
2. Backup vulnerability

24. Complete replication
 A complete copy of DB is maintained at each
site.
 No replication.
ADVANTAGES:
1. Faster and consistent access speeds
2. Reliability
3. Node decoupling
DISADVANTAGES:
1. Update complexity
2. Increased storage requirements

25. Selective Replication
 Combination of partitioning, replication, and
centralization.

26. Functions of DDBMS
 EXTENDED COMMUNIICATION SERVICES: provides access
to remote sites and allow transfer of queries.
 EXTENDED SYSTEM CATALOG: (Global system
catalog) to store data distribution details,
 DUSTRIBUTED QUERY PROCESSING:Translate
request at one site using local DBMS into proper
request to another site using a different DBMS
and data model.
 EXTENDED CONCURRENCY CONTROL: to
maintain concurrency of the replicated data.
 EXTENDED RECOVERY SERVICES: to be able
to recover from individual site crashes and
failure of communication links.

27. TYPES OF DDBMS
marhaba wazir

28. What is it?
Cheerios

29. What is it?
Trail Mix

30. Types of Distributed Database System
 Homogeneous
 Heterogeneous DDBMS
Homogenous Heterogeneous

31. Homogenous Distributed Database Systems
 In this type of database has all data center
have same software
 Much easier to design and manage.
 It appears to user as a single system

32. characteristics
 Data are distributed
 Same DBMS is used
 Data managed by distributed DBMS
 Users access database through one schema
 Global schema is the union of all local DB
schemas

33. Homogeneous Database
Same software

34. Heterogeneous Distributed
Database Systems
In this type of database , Different data center may run different DBMS products,
with possibly different underlying data models.
CHARACTERISICS
• Data is distributed across nodes.
• Different DBMS is used
• Only local access databases can be accomplished using only local DBMS
and schema.
• A global schema exists.

35. Heterogeneous Distributed database
Sql oracle

36. DBMS transparency & Gateways
 Transparency refers to ability to hide the
knowledge that local DBMSs may be
different.
 Applies to heterogeneous environment.
 To achieve transparency, DBMSs at different
sites should support the same interface.

38. Gateways
Gateway provides following functions.
 Protocol for exchange of information between two
DBMSs.
 Mapping between two DBMSs data types.
 Mapping the SQL of the X system to that ofY.
 Mapping feedback information if theY system to
that of the X.
 an effective mechanism to synchronize locking and
commit mechanism ofY system with those
requested by X system.
 Provide relational server function for theY DBMS.

42. http://www.slideshare.net/TAHAROC/types-of-data?from_action=save
 https://www.google.com.pk/search?q=data+allocation+in+distributed+database+syst
ems&espv=2&biw=1440&bih=799&source=lnms&tbm=isch&sa=X&ved=0CAYQ_AUo
AWoVChMI0Oj2vIWJyQIVxDSUCh2jVQ9q&dpr=1
 https://www.google.com.pk/webhp?sourceid=chrome-instant&ion=1&espv=2&
ie=UTF-8#q=horizontal+and+vertical+fragmentation
 http://www.slideshare.net/Loveski/data-replication-in-distributed-system?related=1