DDB_presentation1Database Technologies II

8/17/2019 DDB_presentation1Database Technologies II

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CSM 260

Database Technologies II


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Course Outline

1. Distributed Databases

2. Dimensional Modelling3. Data Warehouse Concets and Design

!. Data Mining


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Te"t #oo$s1. %undamentals o& Database S'stems

%i&th (dition

)ublishers* )earson+,ddison Wesle'

,uthors* (lmasri - a/athe

2. Database S'stems

%ourth (dition

)ublishers* ,ddison Wesle'

,uthors* Thomas Connol' - Carol'n #egg

3. The Data Warehouse Tool$it

Second (dition

)ublishers* Wile'

,uthors* alh imball - Marg' oss


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)art One* Outline

1. Distributed Database Concets

2. Data %ragmentation elication

and ,llocation3. T'es o& Distributed Database

S'stems

!. uer' )rocessing

4. Concurrenc' Control and eco/er'


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Distributed Database Concets

, transaction can be e"ecuted b' multile net5or$edcomuters in a uni&ied manner.

, distributed database (DDB) rocesses nit o&e"ecution 7a transaction8 in a distributed manner. ,distributed database 7DD#8 can be de&ined as

, distributed database 7DD#8 is a collection o&multile logicall' related database distributedo/er a comuter net5or$ and a distributeddatabase management s'stem as a so&t5are

s'stem that manages a distributed database5hile ma$ing the distribution transarent tothe user.


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)arallel Technolog' T5o main t'es o& multirocessor s'stem

architectures

Shared Memor' 7tightl' coule8 architecture.

Multile rocessors share secondar' 7dis$8storage and also share rimar' memor'

Shared dis$ 7loosel' couled8 architecture.

Multile rocessors share secondar' 7dis$8storage but each has their o5n rimar'

memor'.


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)arallel Technolog'

Database management s'stems

de/eloed using the abo/e t'es o&architectures are termed arallel databasemanagement s'stems because the' utilisearallel technolog'

,d/antages

These architectures enable rocessors tocommunicate 5ithout the o/erhead o&e"changing messages o/er a net5or$.


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Shared othing ,rchitecture

(/er' rocessor has its o5n rimar' and

secondar' 7dis$8 memor' no commonmemor' e"ists and the rocessors

communicate o/er a high9seed

interconnection net5or$ 7bus or s5itch8


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Shared othing ,rchitecture


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et5or$ed architecture 7centralised

Database8


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Distributed Database ,rchitecture


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Distributed Database S'stem

,d/antages Management o& distributed data 5ith di&&erent levels

of transparency*

This re&ers to the h'sical lacement o&

data 7&iles relations etc.8 5hich is not$no5n to the user 7distributiontransarenc'8.

The (M):O;(( )O


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,d/antages 7transarenc' contd.8 Distribution and Network transparency* sers do not ha/e to 5orr' about oerational

details o& the net5or$.There is Location transparency, which

refers to freedom of issuing command fromany location without affecting its working

Then there is Naming transparency, whichallows access to any names ob!ect (files,relations, etc) from any location


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? ,d/antages 7transarenc' contd.8

"eplication transparency* It store coies o& data at multile sites.

This is done to minimi>e access time to the

re@uired data.

#ragmentation transparency*

,llo5s to &ragment a relation hori>ontall'

7create a subset o& tules o& a relation8 or

/erticall' 7create a subset o& columns o& a

relation8.


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Other ,d/antages $ncreased reliability and availability*

eliabilit' re&ers to s'stem li/e time that iss'stem is running e&&icientl' most o& the

time. ,/ailabilit' is the robabilit' that thes'stem is continuousl' a/ailable 7usable oraccessible8 during a time inter/al.

, distributed database s'stem has multilenodes 7comuters8 and i& one &ails thenothers are a/ailable to do the Aob.


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Other ,d/antages 7contd.8 $mproved performance*

, distributed D#MS &ragments thedatabase to $ee data closer to 5here it isneeded most.

This reduces data management 7accessand modi&ication8 time signi&icantl'.

%asier e&pansion (scalability)*

,llo5s ne5 nodes 7comuters8 to be addedan'time 5ithout chaining the entirecon&iguration.


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Data %ragmentation elication and ,llocation

Data #ragmentation Slit a relation into logicall' related and

correct arts. , relation can be

&ragmented in t5o 5a's*

'oriontal #ragmentation

ertical #ragmentation


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Data %ragmentation elication and ,llocation 'oriontal fragmentation

It is a hori>ontal subset o& a relation 5hich

contain those o& tules 5hich satis&' selectionconditions.

Consider the (mlo'ee relation 5ith selection

condition 7DO B 48. ,ll tules satis&' thiscondition 5ill create a subset 5hich 5ill be ahori>ontal &ragment o& (mlo'ee relation.

, selection condition ma' be comosed o& se/eralconditions connected b' ,D or O.

Deri/ed hori>ontal &ragmentation* It is the artitioningo& a rimar' relation to other secondar' relations5hich are related 5ith %oreign $e's.



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ertical fragmentation It is a subset o& a relation 5hich is created b'

a subset o& columns. Thus a /ertical &ragmento& a relation 5ill contain /alues o& selectedcolumns. There is no selection condition usedin /ertical &ragmentation.

Consider the (mlo'ee relation. , /ertical &ragmentcan be created b' $eeing the /alues o& ame #dateSe" and ,ddress.

#ecause there is no condition &or creating a/ertical &ragment each &ragment must includethe rimar' $e' attribute o& the arent relation(mlo'ee. In this 5a' all /ertical &ragments o&a relation are connected.

D t % t ti li ti d ,ll ti


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"epresentation

'oriontal fragmentation

(ach hori>ontal &ragment on a relation can beseci&ied b' a Ci 78 oeration in the relational

algebra.

Comlete hori>ontal &ragmentation

, set o& hori>ontal &ragments 5hose conditions C1C2 Cn include all the tules in 9 that is e/er'

tule in satis&ies 7C1 O C2 O O Cn8.

DisAoint comlete hori>ontal &ragmentation* o

tule in satis&ies 7Ci ,D CA8 5here i A. To reconstruct &rom hori>ontal &ragments a

IO is alied.

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DDB_presentation1Database Technologies II