DBMS

11. Give the reasons for allowing concurrency?

The reasons for allowing concurrency is if the transactions run serially, a short transaction may

have to wait for a preceding long transaction to complete, which can lead to unpredictable delays in running a transaction. So concurrent execution reduces the unpredictable delays in running transactions.

12. What is average response time?

The average response time is that the average time for a transaction to be completed after it has

been submitted.

13. What are the two types of serializability?

The two types of serializability is

Ø Conflict serializability

Ø View serializability

14. Define lock?

Lock is the most common used to implement the requirement is to allow a transaction to access a data item only if it is currently holding a lock on that item.

15. Define deadlock?

Ø Exclusive

Neither of the transaction can ever proceed with its normal execution. This situation is called deadlock.

18. Define the phases of two phase locking protocol

Growing phase: a transaction may obtain locks but not release any lock.

Shrinking phase: a transaction may release locks but may not obtain any new locks.

19. Define upgrade and downgrade?

It provides a mechanism for conversion from shared lock to exclusive lock is known as upgrade. It provides a mechanism for conversion from exclusive lock to shared lock is known as

downgrade.

20. What is a database graph?

The partial ordering implies that the set D may now be viewed as a directed acyclic graph, called

a database graph. 

20. What are the two methods for dealing deadlock problem?

The two methods for dealing deadlock problem is deadlock detection and deadlock recovery.