DFC20283 CHAPTER 5 (5.1.6-5.1.9)

What is the purpose of concurrency control in database management?

• To ensure atomicity of transactions

• To manage simultaneous access to data by multiple transactions

• To allow faster database queries

• To reduce the size of the database

Which of the following is a problem caused by concurrency control?

• Referential integrity

• Data redundancy

• Uncommitted data

• Deadlocks

Which method is used in concurrency control to ensure transactions are serialized?

• Two-phase locking

• COMMIT

• Lost update

• Rollback

What is meant by "lock granularity" in concurrency control?

• The time taken to acquire a lock

• The priority of one lock over another

• The number of locks used in a transaction

• The size of the data item that a lock can be applied to

Which of the following best describes a "deadlock" in database transactions?

• A transaction that completes successfully but is not committed

• A situation where a transaction waits indefinitely due to another transaction holding a lock on a resource

• A scenario where a database is locked for too long

• A process of ensuring serializability of transactions

What does "inconsistent retrieval" mean in terms of concurrency control?

• Data from different transactions are merged into one

• Data is retrieved but not locked during the process

• A transaction reads data that has already been committed

• Data is read while it is being modified by another transaction, resulting in inconsistent or incorrect data

A transaction updates a record, but before it commits, another transaction reads the uncommitted data. Which concurrency problem does this describe?

• Lost update

• Deadlock

• Uncommitted data

• Inconsistent retrieval

In a database system, you are using two-phase locking. What would happen if a transaction attempts to acquire a new lock after it has already released a lock?

• It will enter a deadlock state

• It will violate the rules of two-phase locking

• It will automatically commit the transaction

• It will result in a lost update

Which of the following scenarios requires database recovery management?

• A transaction has failed and data needs to be restored

• A lock granularity issue prevents a transaction from completing

• Multiple transactions are waiting for resources

• Data is committed without being locked

You are tasked with performing a database backup as part of recovery management. What is the primary reason for this process?

• To improve transaction speed

• To allow concurrency control

• To improve lock granularity

• To ensure data can be restored in case of system failure