Distributed Database Systems Quiz 2

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Questions and Answers

What is the main purpose of concurrency control algorithms in a distributed database system?

  • Manage data replication in the database system
  • Enforce isolation property for concurrent transactions (correct)
  • Optimize query processing and optimization
  • Ensure atomicity and durability of transactions

Which aspect of reliability do reliability measures in a distributed database system primarily enforce?

  • Atomicity and durability (correct)
  • Query optimization
  • Consistency
  • Integrity enforcement

What is the main function of distributed transaction processing in a distributed database system?

  • Optimize query processing and optimization
  • Enforce isolation property for concurrent transactions
  • Maintain consistency and reliability of transactions across multiple sites (correct)
  • Manage data replication in the database system

In a distributed database system, what does data replication primarily aim to achieve?

<p>Enhance fault tolerance and availability of data (C)</p> Signup and view all the answers

What is the primary role of web data management in a distributed database system?

<p>Ensure efficient storage and retrieval of web-related data (C)</p> Signup and view all the answers

What is the purpose of assigning unique timestamps to transactions in a distributed DBMS?

<p>To establish a serialization order and execute transactions accordingly (C)</p> Signup and view all the answers

What is the preferred method for assigning timestamps in a distributed DBMS to maintain uniqueness?

<p>Use local counters with site identifiers appended for uniqueness (B)</p> Signup and view all the answers

What is the purpose of the basic timestamp ordering (TO) algorithm?

<p>To execute operations as soon as they are received, without causing deadlocks (A)</p> Signup and view all the answers

In the basic TO algorithm, when is a new operation accepted by the scheduler?

<p>If the new operation's transaction is younger than all conflicting ones already scheduled (A)</p> Signup and view all the answers

What distinguishes the conservative TO algorithm from the basic TO algorithm?

<p>It causes operations to wait instead of restarting them (C)</p> Signup and view all the answers

Flashcards

Concurrency Control Purpose

To enforce the isolation property, ensuring that concurrent transactions do not interfere with each other, maintaining data consistency.

Reliability Measures Enforce

They primarily enforce atomicity (all or nothing) and durability (changes are permanent) of transactions in the face of failures.

Distributed Transaction Processing Function

To maintain the consistency and reliability of transactions by coordinating them across multiple database sites.

Data Replication Aim

To enhance fault tolerance by allowing the system to continue operating even if some data copies are unavailable, and to improve data availability for faster access.

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Web Data Management Role

To ensure efficient storage, retrieval, and management of data related to web applications and services in a distributed environment.

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Unique Timestamps Purpose

To establish a clear order for executing transactions, ensuring serializability and preventing conflicts in a distributed system.

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Timestamp Assignment Method

Combine local counters with a unique site identifier to guarantee uniqueness across the entire distributed system.

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Basic TO Algorithm Purpose

To execute operations as soon as they are received without waiting, and to avoid deadlocks.

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Operation Acceptance Condition

If the transaction timestamp of the new operation is later (younger) than all conflicting operations that have already been scheduled.

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Conservative TO vs. Basic TO

The conservative TO algorithm makes operations wait if there is a risk of conflicting with older transactions, whereas the basic TO algorithm would restart them.

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Study Notes

Concurrency Control Algorithms

  • Ensure that database transactions are executed in a correct and consistent manner, maintaining data integrity and consistency in a distributed database system.

Reliability Measures

  • Primarily enforce fault tolerance, ensuring that the system can recover from failures and continue to operate correctly.

Distributed Transaction Processing

  • Enables multiple operations to be executed as a single, all-or-nothing unit of work, ensuring consistency and reliability across the distributed system.

Data Replication

  • Aims to achieve high availability and improved system performance by maintaining multiple copies of data in different locations.

Web Data Management

  • Plays a crucial role in managing and integrating web-based data sources, enabling efficient and effective data retrieval and processing.

Assigning Unique Timestamps

  • Enables the ordering of transactions, ensuring that the correct sequence of operations is maintained, and preventing conflicts and inconsistencies.

Assigning Timestamps

  • The preferred method is to use a centralized timestamp generator, which ensures uniqueness and avoids conflicts.

Basic Timestamp Ordering (TO) Algorithm

  • Ensures that transactions are executed in a consistent and correct order, by assigning timestamps to transactions and ordering them based on these timestamps.

Basic TO Algorithm

  • A new operation is accepted by the scheduler if its timestamp is greater than the previous operation's timestamp.

Conservative TO Algorithm

  • Distinguishes from the basic TO algorithm by using a more conservative approach, where an operation is only accepted if its timestamp is greater than the previous operation's timestamp, and the operation does not conflict with any previously scheduled operations.

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