week 3 - Why Distribution?

Question 1

Four items that make up a distributed database system

Answer 1

1) Availability
2) Scalability
3) Reliability/ Fault Tolerance
4) Transparency

Question 2

Why do corporations use distribution in databases?

1) It prevents data collisions for quicker updates.
2) It helps by allowing a better understanding of data around data within an organization.
3) Distributed databases can avoid large traffic because the replicated data can be accessed locally.

Answer 2

3) Distributed databases can avoid large traffic because the replicated data can be accessed locally.

Question 3

1.Question 1

What does transparency refer to in database terminology?

1) Separation of higher level semantics of a database system from the lower level implementation issues.
2) The ability of users to see the details of how a database system works.
3) The ability of users to manage the details of lower level database implementation.
4) The ability of users to see where pieces of data are stored in a distributed database system.

Answer 3

1) Separation of higher level semantics of a database system from the lower level implementation issues.

Question 4

What does scalability refer to in database terminology?

1) The ability of a database system to expand and serve more users.
2) The ability of a database system to provide faster access speed.
3) The ability of a database system to provide better access with a minimum quality of service guarantee.
4) The ability of a database system to provide the same level of service with a lower cost.

Answer 4

1) The ability of a database system to expand and serve more users.

Question 5

What is Horizontal Fragmentation

Answer 5

Split rows of the table into two(+) rows

say half the rows go into one table and half go into another table

Question 6

What is Vertical Fragmentation

Answer 6

Spit columns of the table into two(+) tables

Question 7

Which comes first Fragmentation or Replication

Answer 7

Fragmentation

Question 8

Three main properties of good Fragmentation

Answer 8

1) Completeness
2) Reconstruction
3) Disjointness

Question 9

Completeness of Fragmentation

Answer 9

no data item would be lost

Question 10

Reconstruction of Fragmentation

Answer 10

You need some element that you can use to create the relationship

Question 11

Disjointness of Fragmentation

Answer 11

No supplicates

Question 12

Why is fragmentation a useful concept in distributed database design?

1) It makes data easier to store through data chunking.
2) It reduces disk space utilization and allows for easy access to data.
3) It allows data to be quickly archived in the cloud.

Answer 12

2) It reduces disk space utilization and allows for easy access to data.

Question 13

database selection symbol

Answer 13

Sigma(σ)

Question 14

simple predicates

Answer 14

From original table (R) (maybe what they are using to for a key)

Question 15

minterm predicates

Answer 15

What are the fragments (what you use to filter out the selection ?)

Question 16

Derived Horizontal Fragmentation

Answer 16

Derived Horizontal Fragmentation
Is defined on a member relation of a link according to a selection operation specified on its owner• It is important to remember two points – First, the link between the owner and the member relations is defined as an equi-join

Create new join tables

Question 17

Two advantages of replication

Answer 17

1) Increased availability

2) Faster query evaluation

Question 18

3 Disadvantage of f replication

Answer 18

1) Updates are challenging
2) Transaction processing
3) Concurrency control can be an issue

Question 19

What is a sharded deployment of a database?

1) A partial replication where each fragment resides at one site.
2) Each fragment resides in one site only.
3) A full replication where each fragment resides at each site.

Answer 19

2) Each fragment resides in one site only.

Question 20

Is replication good if you have a lot of queries

Answer 20

Yes

Question 21

What is the main disadvantage of full replication?

1) It requires less disk space to perform.
2) The process to perform a single update is slower since it must be updated on different databases to keep the copies consistent.
3) There is less data movement over a network.

Answer 21

2) The process to perform a single update is slower since it must be updated on different databases to keep the copies consistent.

Question 22

Best Questions 3 for placement of Fragments

Answer 22

1) minimize query response time
2) maximize throughout?
3) minimize some cost?