Week 12 Part 2

Question 1

This stores multiple copies of a dataset on multiple nodes

Answer 1

Replication (the copies are called replicas)

Question 2

What does replication provide?

Answer 2

Scalability and availability

Question 3

The redundancy achieved through replication leads to _____ tolerance

Answer 3

fault tolerance

Question 4

What are the 2 methods used to implement replication?

Answer 4

Master-slave

peer-to-peer

Question 5

Master-slave replication: All data is written to a master node, what happens?

Answer 5

The slave nodes replicate the data

Question 6

Master-slave replication: Where do write requests like insert, delete, and update occur? Where do read requests occur?

Answer 6

Write requests: Master
read requests: Slave

Question 7

Is master-slave replication ideal for write intensive loads or read intensive loads? Why?

Answer 7

Read intensive loads. The system can be scaled horizontally by adding more slave nodes.

Question 8

What happens to the master slave replication system when the amount of writes increases?

Answer 8

The system suffers. There’s only 1 master node.

Question 9

T/F - If the master node fails, reads are no longer possible

Answer 9

False, can read from any slave node

Question 10

T/F - A salve node can be configured as a backup for the master node

Answer 10

True

Question 11

T/F - If the master node fails, writes are no longer possible

Answer 11

True, until a master node is reestablished

Question 12

T/F - master node is either resurrected from a backup of the master node, or a new
master node is chosen from the slave nodes

Answer 12

True

Question 13

T/F - In peer to peer, one node writes, the other reads

Answer 13

False

Question 14

T/F - In P2P each write is copied by all peers

Answer 14

True

Question 15

Name this ACID principle: ensures that all operations will always succeed or fail
completely (no partial transactions)

Answer 15

Atomicity

Question 16

Name this ACID principle: ensures that the database will always remain in a consistent
state by ensuring that only data that conforms to the constraints of the
database schema can be written to the database

Answer 16

Consistency

Question 17

Name this ACID principle: ensures that the results of a transaction are not visible to other
operations until it is complete

Answer 17

Isolation

Question 18

Name this ACID principle: ensures that the results of an operation are permanent. In other
words, once a transaction has been committed, it cannot be rolled back.
This is irrespective of any system failure

Answer 18

Durability

Question 19

A user updates 3 records. 2 are successful, the 3rd one fails. The entire system is rolled back before the update. Why?

Answer 19

Atomicity

Question 20

User tries to update a column with a datatype of float with a varchar value. The DB rejects this update. Why?

Answer 20

Consistency

Question 21

user A attempts to update 2 records, the DB updates the first one, but User B tries to update the 2nd record at the same time. User B cannot update the 2nd record. Why?

Answer 21

Isolation (must wait until User A’s update succeeds or fails)

Question 22

A user updates a record, the DB updates it. Right after this there is a power failure but the DB maintains its state. When the power comes back on the record is still there, why?

Answer 22

Durability