Transactions

Question 1

What is an major objective in developing a database?

Answer 1

A major objective in developing a database is to enable many

users to access shared data concurrently (samtidigt).

Question 2

What is Transaction processing?

Answer 2

Transaction processing is a style of computing that divides work
into individual,indivisible operations called transactions.

Question 3

what does Transaction processing systems attempt to provide?

Answer 3

Transaction processing systems attempt to provide fast and

predicable response time to requests

Question 4

what is Transaction processing designed for?

Answer 4

Transaction processing is designed to maintain a system’s
integrity in a known, consistent state, by ensuring that
interdependent operations on the system are
- either all completed successfully or
- all cancelled successfully

Question 5

What is the definition of Concurrency control?

Answer 5

Definition of Concurrency control:

• The process of managing simultaneous operations on the database
  without having them interfere with one another.

Question 6

What is a transaction?

Answer 6

Informally: A transaction is an execution of a program that accesses a shared database

Question 7

what is The objective of a concurrency control protocol?

Answer 7

The objective of a concurrency control protocol is to schedule transactions in such
a way as to avoid any interference between them:

Question 8

What is one obvious solution to reach the objective of a concurrency control protocol ?

Answer 8

One obvious solution to reach the concurrency control protocol objective is to allow ONLY ONE transaction at the time to execute:

Question 9

What are the pros and cons of Locking?

Answer 9

Locking Protocols
\+ good for update intensive 
   applications
- locking overheads
- not free from deadlock

Question 10

What are the pros and cons of Timestamping?

Answer 10

Timestamp Protocols
\+Freedom from deadlocks
\+No transaction has to wait 
  for other transaction
\+Transactions do not block 
  each other
  => better concurrency than 
  locking protocols
\+An aborted transaction is 
  restarted with a new 
  timestamp

- Can result in starvation of 
  long transaction:
  — a long transaction can be 
  restarted all the time and 
  never be completed
  if shorter transactions 
  completes all the time

Question 11

What does ACID stand för?

Answer 11

A = Atomicity
C = Consistency
I = Isolation
D = Durability