ADBMS unit 4: distributed database design (DDD)

Question 1

Explain what are distributed database in short

Answer 1

A distributed System is a collection of autonomous computer systems that are physically separated but are connected by a centralized computer network that is equipped with distributed system software.

Question 2

whare are distributed databases used

Answer 2

These are used in numerous applications, such as online gaming, web applications, and cloud computing.

Question 3

Design issues intro

Answer 3

However, creating a distributed system is not simple, and there are a number of design considerations to take into account. The following are some of the major design issues of distributed systems.

Question 4

explain design issues in distributed databases

Answer 4

scalability

reliability

availability

consistency

latency

load balancing

security

architectural design patterns

communication issues

data management

Question 5

explain challenges in scalability

Answer 5

handling increases load: as no. of users or requests increases, the system must scale accordingly without performance degradation

Question 6

explain geographic distribution

Answer 6

ensuring performance across geographically dispersed locations

Question 7

strategies to achieve scalability

Answer 7

horizontal scaling

vertical scaling

sharding

Question 8

explain horizontal scaling

Question 9

explain vertical scaling

Question 10

explain sharding

Question 11

explain reliability

Question 12

what is fault tolerance in reliability

Question 13

explain redundancy and replication

Question 14

explain availability

Question 15

explain consistency

Question 16

explain latency

Question 17

explain load balancing

Question 18

explain security

Question 19

explain architectural design patterns

Question 20

explain communication issues

Question 21

explain data management

Question 22

what is fragmentation

Answer 22

breaking a global relation R into smaller relations called framgents R1, R2, ….. Rn such that these smaller relations contain enough information to reconstruct the global relation R

Question 24

types of fragmentation

Answer 24

1. horizontal
   primary
   derived
2. vertical
3. hybrid

Question 25

explain horizontal fragmentation

Answer 25

breaking a global relation R horizontally ( with respect to data stored ) into two or more sub-relations without disturbing the structure of the relation is called Horizontal fragmentation.

Schema(R) = Schema(R1) = Schema(R2) = Schema(Rn)

Question 26

example of Horizontal fragmentation
Student table / relation

with columns
reg_no
name
gender
address
contact
campus

divide this table using campus property

Answer 26

if there are three types of values in campus column then we can divide this table into three horizontally fragments

Question 27

what do we divide in horizontal frag. rows or column

Answer 27

in horizontal fragmentation we divide columns only not rows

Question 28

what operation we called it when we perform horizontal fragmentation

Answer 28

horizontal fragmentation is just a SELECTION operation performed on the global relation R with appropriate selection conditions P

Question 30

what are correctness rules of fragmentation

Answer 30

when we divide global relation R into numerous fragments, to check whether this fragments are correct or not we have some rules which are known as correctness rules

Question 31

explain completeness, first rule of correctness of fragmentation

Answer 31

breaking of relation R into sub-relations R1, R2, … Rn is said to be complete if and only if each data item (record) present in R can also be found in some Ri

Question 32

what is rule for horizontal to completness

Answer 32

for horizontal and vertical fragmentation
R1, R2, … , Rn belongs to R

Question 33

explain completeness in simple words

Answer 33

when we add all fragments, we should get original table

Question 34

explain reconstruction

Answer 34

if a global relation R is broken into fragments R1, R2, … Rn. then there should be a way to reconstruct R from these fragments without loosing data.

Question 35

For horizontal fragmentation, how does reconstruction works

Answer 35

R1 union R2 union Rn = R

Question 36

for vertical fragmentation what operation we perform to get original table back

Answer 36

R1 inner_join R2 inner_join R3 inner_join Rn = R

Question 37

in horizontal fragmentation what operation we perform to get original table / relation back

Answer 37

union operation

Question 38

for vertical fragmentation which operation we perform to get original table / relation back

Answer 38

natural join

Question 39

explain disjointness rule of correctness of fragmentation

Answer 39

if a global relation R is broken into fragments R1, R2 and Rn, a record (row) that is found in one fragment must not present in any other fragments.

That is,

R1 ∩ R2 ∩ … R3 = NULL

===

Fragmented record must not found into other fragments

No records must be common in more than one fragment

Question 40

what are two types of horizontal gragmentation

Answer 40

primary
secondary

Question 41

explain primary horizontal fragmentation.
1. What is it?
2. What do we require?
3. How to find the simple conditions?

Answer 41

1. It is about fragmenting single table horizontally with set of simple conditions
2. The procedure to find the simple conditions that are required to fragments the table.
3. Simple predicates
   Min-term predicates

Question 42

what do we require to achieve primary horizontal fragmentation

Question 43

how to find simple conditions, for primary horizontal fragmentation

Answer 43

simple predicates
min-term predicates

before that we need to know, application or set of applications that are going to access these fragments differently

Question 44

what are simple predicates

Answer 44

Given a relation R with set of n attributes, a simple predicate P is a condition of the form as follows:
attribute i comparison-operator value

here,
1. attribute is any attribute of the relation R
2. comparison operator can be one of =, <, >, >=, <=, !=
3. value is the permitted value for the domain of that attribute

Example:
REG_NO = 119
GENDER = ‘M’
GRADE = 5

Question 45

explain set of simple predicates

Answer 45

a relation usually fragmented using multiple simple predicates collectively

Example:

Employee(Emp_id, Ename, Department, Office)
p = {office=’chennai’, department=’design’}

Question 46

what are some desirable properties of simple predicates

Answer 46

the set of simple predicates should be complete and minimal

Complete: not missing any data and equal probability of access by every application

Minimal: If all the predicates of a set P are relevant, then P is minimal. That is, there should be at least one application that accesses fragments f1 and f2 differently

Question 47

what are min-term predicates

Answer 47

Time: 18:45

https://www.youtube.com/watch?v=W0BSpV4bM74&t=29s

Question 48

can we use simple predicates for fragmentation directly

Answer 48

no

Question 49

what is min-term predicate

Question 50

formal definition of min-term predicate

Question 51

What is Derived horizontal framgentation

Answer 51

The process of creating horizontal fragments of a table in question based on the already created horizontal fragments of another relation (for example, base table) is called Derived Horizontal Fragmentation

PK = owner relation
FP = member relation

Question 52

what is semi-join

Answer 52

semi-join is a join operation that results in a structure and records of one table that match with the records of the other table

Question 59

resource: derived horizontal fragmentation

Answer 59

https://www.youtube.com/watch?v=CF9gXrOXAxI&t=250s

Question 60

resources

Answer 60

https://www.ques10.com/p/17566/explain-design-issue-of-distributed-database-1/

Question 61

data allocation

Answer 61

https://www.ques10.com/p/17566/explain-design-issue-of-distributed-database-1/