DBMS Advanced Features and Distributed Databases

What is the purpose of query optimization in a DBMS?

• To ensure that queries are executed using the least amount of resources.

• To create as many different execution plans as possible.

• To simplify SQL queries for easier reading.

• To enhance the security of database queries.

Answer explanation

The purpose of query optimization in a DBMS is to ensure that queries are executed using the least amount of resources, improving performance and efficiency. This is crucial for handling large datasets effectively.

Which of the following is NOT an ACID property?

• Atomicity

• Consistency

• Isolation

• Accessibility

Answer explanation

The ACID properties of a database transaction are Atomicity, Consistency, and Isolation. Accessibility is not one of these properties, making it the correct answer as it does not pertain to the ACID principles.

In the context of transaction management, what does the term 'Durability' mean?

• Transactions can be reversed at any time.

• Changes made by committed transactions are permanent and cannot be undone.

• Transactions are only temporarily stored in the database.

• Transactions must be processed within a short duration.

Answer explanation

In transaction management, 'Durability' ensures that once a transaction is committed, its changes are permanent and will survive system failures. This means they cannot be undone, making the correct choice about durability.

Which technique involves assigning security permissions based on user roles within an organization?

• Discretionary Access Control

• Mandatory Access Control

• Role-Based Access Control (RBAC)

• Attribute-Based Access Control

Answer explanation

Role-Based Access Control (RBAC) assigns security permissions based on user roles, making it easier to manage access rights according to the responsibilities and functions of users within an organization.

Which optimization technique relies on rules of thumb rather than detailed cost estimates?

• Cost-Based Optimization

• Heuristic-Based Optimization

• Rule-Based Optimization

• Statistical Optimization

Answer explanation

Heuristic-Based Optimization uses general rules of thumb to make decisions, rather than relying on detailed cost estimates. This approach allows for quicker, more flexible solutions in optimization problems.

In distributed database systems, what is the primary purpose of data replication?

• To ensure data availability and fault tolerance across different locations.

• To minimize the number of copies of data.

• To reduce the load on a single server.

• To eliminate the need for data backups.

Answer explanation

The primary purpose of data replication in distributed database systems is to ensure data availability and fault tolerance across different locations, allowing systems to remain operational even if one or more nodes fail.

What does the 'C' in the CAP Theorem stand for?

• Consistency

• Concurrency

• Connectivity

• Control

Answer explanation

In the CAP Theorem, the 'C' stands for Consistency. This means that every read receives the most recent write or an error, ensuring that all nodes in a distributed system reflect the same data at the same time.

Which recovery technique involves periodically saving the state of the database to reduce recovery time after a failure?

• Rollback/Undo Recovery

• Commit/Redo Recovery

• Checkpoint Recovery

• Transaction Log Backup

Answer explanation

Checkpoint Recovery involves periodically saving the state of the database, allowing for faster recovery after a failure by restoring to the last saved state instead of processing all transactions from the beginning.

What is a primary advantage of using a distributed database system?

• Easier application development at multiple locations.

• Simplified database management.

• Reduced need for data encryption.

• Lower initial setup costs.

Answer explanation

A primary advantage of distributed database systems is that they facilitate easier application development at multiple locations, allowing teams to work collaboratively and access data locally, enhancing efficiency and responsiveness.

How does Role-Based Access Control (RBAC) improve database security?

• By encrypting all data by default.

• By assigning permissions based on the roles users hold in an organization.

• By limiting database access to only administrators.

• By requiring multi-factor authentication for all users.

Answer explanation

RBAC enhances database security by assigning permissions based on user roles, ensuring that individuals only have access to the data necessary for their job functions, thus minimizing the risk of unauthorized access.