Distributed Database Management Systems: Lecture 13

Distributed Database
Management Systems

Lecture 13


How
Interests of the local and head offices
mar result following vertical
partitions of this table:
EMP1(eId, eName, eDept)
EMP2(eId, eQual, eSal)

Virtual University of Pakistan

2


1- Vertical; Different subsets of
attributes are stored at different
places, like,
Table EMP(eId, eName, eDept, eQual,
eSal)

Virtual University of Pakistan

3


Interests of the local and head offices may
result following vertical partitions of this

table:
EMP1(eId, eName, eDept)
EMP2(eId, eQual, eSal)

Virtual University of Pakistan

4


CLIENT
(cAC#, cName, cAdr, cBal) table is
placed in different databases based on
their location, like from Lahore, Pindi,
Karachi, Peshawar, Quetta

Virtual University of Pakistan

5


3- Degree of Fragmentation
Between no to the extreme level that
could be to the individual tuple or
column level; a compromised decision

Virtual University of Pakistan

6

4- Correctness Rules for
Fragmentation

Virtual University of Pakistan

7


• Completeness: each of the data item
(a tuple or a attribute) that can be in R
can also be in one or more Ri
∀ x ∈ R, ∃ Ri such that x ∈ Ri
Resembles Lossless decomposition
property in Normalization

Virtual University of Pakistan

8


• Reconstruction: it should be
possible to define a relational
operator such that the original
relation can be reconstructed
R = g(R1, R2, …, Rn)
Reconstruction ensures that the
dependencies of the original
relation are preserved in
fragmentation
Virtual University of Pakistan

9


• Disjoint ness:
if data item x is in Rj, it is not in
any other fragment
∀ x ∈ Ri, ∃ Rj such that x ∈ Rj, i ≠
j

Virtual University of Pakistan

10


• Allocation Strategy:
Partitioned, fully or partially
replicated; depends mainly on
requirements

Virtual University of Pakistan

11


Horizontal Fragmentation

Virtual University of Pakistan

12

• Partitions a table along its tuples
• is performed based on some
Predicate/ Condition

Virtual University of Pakistan

13


Primary Horizontal
Fragmentation(PHF)

Virtual University of Pakistan

14


Information Requirements

Virtual University of Pakistan

15


Database Information: We may
need to consult the conceptual
DB design
RDM being Semantically not that

rich
Apart from tables, we need
relationships, cardinality and the
owner and member tables
Virtual University of Pakistan

16


PAY

EMP

title, sal

owner = PAY
member = EMP

eNo, Name, title

ASIGN

Virtual University of Pakistan

jNo, jName, budget, loc

eNo, jNo, resp, dur

17

PROJ


Application Requirement

Virtual University of Pakistan

18