Client-Server Database Model Quiz

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Questions and Answers

What is the primary goal of commitment ordering in transaction management?

To serialize all transactions to avoid any processing conflicts.

To use timestamps to manage the order of transaction execution.

To prioritize the execution order of transactions to prevent deadlocks. (correct)

To ensure that all database transactions are processed simultaneously.

How do record locks improve the booking process in airline reservations?

They prevent users from booking seats if another user is processing a transaction.

They lock the entire flight schedule to enhance security.

They allow multiple users to book different seats at the same time. (correct)

They ensure that seats cannot be held for an extended period.

What is a significant downside of using serialization in transaction management?

It guarantees that no transactions are ever processed concurrently.

It causes frustration by failing transactions when seats are sold out. (correct)

It requires extensive database resources to maintain a serialized state.

It significantly enhances the speed of all transactions.

What is a drawback of timestamp ordering in transaction management?

It requires frequent timestamp checks, leading to inefficiency. Signup and view all the answers

Which of the following statements is true regarding the lessons learned from airline booking systems?

There are important trade-offs and considerations in each management method. Signup and view all the answers

What is one of the main responsibilities of the server in the Client-Server Database model?

Fetch data and push it back to clients Signup and view all the answers

Which of the following describes the lost update problem?

Overwritten updates by multiple clients lead to data loss Signup and view all the answers

What solution prevents multiple clients from modifying data at the same time?

Record locks Signup and view all the answers

How does serialization address issues with concurrent access?

It executes transactions in a strictly sequential order Signup and view all the answers

Which method involves using timestamps to manage transaction operations?

Timestamp Ordering Signup and view all the answers

What is a significant drawback of concurrent access in a database system?

Potential for lost updates and data conflicts Signup and view all the answers

What can result if resources are exhausted during serialization?

Transaction failures Signup and view all the answers

In the Client-Server Database model, which of the following is NOT a benefit?

Direct client database access Signup and view all the answers

Study Notes

Client Server Database Model

Client-Server Database model utilizes a dedicated server to store and execute the Database Management System (DBMS) within a network environment.
Clients access the DBMS through the server.
Clients rely on the server for database access, lacking direct interaction with the database.
Servers process requests, retrieve data, and transmit it back to clients.
Benefits include multi-user access, enabling concurrent access by multiple users.
Access is unrestricted, enabling various users and applications to interact simultaneously.
Concurrent access introduces challenges with simultaneous data retrieval, updates, and insertions.

Problems With Concurrent Access

Lost update problem: Occurs when multiple clients simultaneously update data, potentially causing one client to overwrite another's changes, leading to data loss.
Example Lost Update Problem: Three travel agencies (London, Birmingham, Swindon) with data stored in London.
Birmingham and Swindon simultaneously access the data.
Birmingham sells 3 seats.
Swindon sells 5 seats, overwriting Birmingham's update due to differing processing times.
Birmingham's update is lost, demonstrating the lost update problem.

Solutions for Lost Update Problem

Record locks: The DBMS locks specific data records (e.g., available seats) during modification. This ensures only one client can modify the data at a time, preventing concurrent updates.
Serialization: Transactions are processed sequentially in the order they are received. Guarantees data integrity but can lead to transaction failures if resources are depleted (e.g., all seats sold out).
Timestamp Ordering: Each transaction includes a read and write timestamp. If a transaction modifies data that has been read and written to since the previous timestamp, the write attempt fails. The transaction restarts with the updated data.
Commitment Ordering: An algorithm evaluates transaction characteristics and prioritizes transactions to prevent deadlocks and conflicts.

Applying Solutions to Airline Bookings

Record locks: For individual seats instead of the whole database, enabling concurrent bookings for separate seats.
Record locks: The lock is temporary, releasing it if a booking isn't completed within a period (e.g., 15 minutes).
Serialization: Transactions might fail when all seats are sold, potentially causing customer frustration when trying to book different flights concurrently.
Timestamp ordering: Implementing this needs frequent timestamp checks, leading to computational overhead, thus potentially making it impractical for airline booking systems.

Conclusion

The lesson explains the client-server database model, concurrent access challenges, and solutions like record locks, serialization, timestamp ordering, and commitment ordering.
It highlights solutions' practical applications in airline bookings, showcasing the trade-offs and real-world considerations of each method.

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Description

Test your knowledge on the Client-Server Database model and its functionalities. This quiz will cover topics such as the role of servers, benefits of multi-user access, and problems associated with concurrent access. Challenge yourself with examples like the lost update problem.