BrAinY 4Presented to:- Ma’am Asima Jamil & Class

GROUP MEMBERSZupashSanaMarhabaGROUP LEADER Hira Anwar

DISTRIBUTED DATABASES

OUR TOPIC OF PRESENTATION IS

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

Centralized DB system Distributed DB system Decentralized DB system Distributed DBMS

Presented by

ZUPASH KIRAMAT

Centralized Database systemA 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

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.

Distributed DB system

Difference

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

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.

ADVANTAGES AND DISADVANTAGES

SANA AYUB

ADVANTAGES

Local control Reliability and availability Efficient querying process Modular growth Economics

Advantages…

Disadvantages

Software complexity and high costs

Processing overheads Data integrity Complex DB design Slow response

DISTRIBUTED DB DESIGN

HIRA ANWAR

Distributed DB designThree additional factors are involved

1.Data Fragmentation2.Data replication3.Data allocation

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.

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

41

Horizontal and Vertical Fragmentation

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.

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 replication3. Selective replication

Fragmented data allocation. Database partitioned into disjoint fragments,

each fragment assigned to one site. Also called non-redundant allocation or

partitioned allocation.

Advantages:1. Efficiency2. SecurityDisadvantages3. Inconsistent access speeds4. Backup vulnerability

Complete replication A complete copy of DB is maintained at

each site. No replication.

ADVANTAGES:1. Faster and consistent access speeds2. Reliability3. Node decouplingDISADVANTAGES:4. Update complexity5. Increased storage requirements

Selective Replication Combination of partitioning, replication,

and centralization.

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.

TYPES OF DDBMS

marhaba wazir

What is it?

Cheerios

What is it?

Trail Mix

Types of Distributed Database System

Homogeneous Heterogeneous

DDBMS

Homogenous

Heterogeneous

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

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

Homogeneous Database

Same software

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.

Heterogeneous Distributed database

Sql oracle

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.

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 of Y. Mapping feedback information if the Y system to

that of the X. an effective mechanism to synchronize locking

and commit mechanism of Y system with those requested by X system.

Provide relational server function for the Y DBMS.

http://www.slideshare.net/TAHAROC/types-of-data?from_action=save https://

www.google.com.pk/search?q=data+allocation+in+distributed+database+systems&espv=2&biw=1440&bih=799&source=lnms&tbm=isch&sa=X&ved=0CAYQ_AUoAWoVChMI0Oj2vIWJyQIVxDSUCh2jVQ9q&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