Master Concurrency Control in Distributed Systems: A Comprehensive Guide

Question 1

Which of the following is NOT a potential issue that can occur when using locks in concurrency control?

Accepted Answer

Data integrity violations

Answer

Deadlock

Answer

Starvation

Answer

Race conditions

Question 2

What is the key difference between a monitor and a semaphore in concurrency control?

Accepted Answer

Monitors provide mutual exclusion and semaphores only provide resource counting.

Answer

Semaphores provide mutual exclusion and monitors only provide resource counting.

Answer

Monitors can be used for both mutual exclusion and resource counting, while semaphores are only used for resource counting.

Answer

There is no difference between a monitor and a semaphore.

Question 3

What is the primary purpose of the timestamp ordering protocol in distributed systems?

Accepted Answer

To ensure that messages are delivered in the order they were sent.

Answer

To prevent lost messages.

Answer

To detect and recover from network partitions.

Answer

To ensure that all replicas of a distributed system are consistent.

Question 4

What does the CAP theorem state about distributed systems?

Accepted Answer

A distributed system can only satisfy two out of three properties: consistency, availability, and partition tolerance.

Answer

A distributed system can only guarantee consistency and availability.

Answer

A distributed system can only guarantee availability and partition tolerance.

Answer

A distributed system can only guarantee consistency and partition tolerance.

Question 5

Which of the following is a primary advantage of utilizing locks in distributed systems?

Accepted Answer

Ensures exclusive access to shared resources, preventing concurrent modifications

Answer

Improves system performance by reducing contention and resource conflicts

Answer

Eliminates the necessity for implementing synchronization mechanisms

Answer

Guarantees the absence of deadlocks in the system

Question 6

What is the fundamental purpose of employing semaphores in a distributed system?

Accepted Answer

To control and regulate access to shared resources, ensuring orderly utilization

Answer

To synchronize the execution of multiple threads, coordinating their activities

Answer

To efficiently manage memory allocation and resource distribution

Answer

To detect and resolve deadlock situations, preventing system failures

Question 7

Identify a potential drawback associated with the implementation of monitors in distributed systems:

Accepted Answer

Increased overhead due to message passing and communication latency

Answer

Limited scalability as the number of participating nodes grows

Answer

Complexity in implementation and maintenance, requiring specialized expertise

Answer

High susceptibility to deadlocks, making system recovery challenging

Question 8

Define the concept of starvation in the context of concurrency control:

Accepted Answer

A situation where a process indefinitely waits for a resource, unable to progress

Answer

A scenario where a process is granted access to a resource ahead of another with higher priority

Answer

A condition where a process cannot acquire a resource due to deadlocks

Answer

A circumstance where a process is forcibly terminated due to excessive resource consumption

Question 9

Define livelock in a distributed system and explain the common causes that can lead to it.

Accepted Answer

A condition where multiple processes are continuously exchanging resources, but none are making progress.

Answer

A state where a process is permanently blocked due to resource starvation.

Answer

A situation where processes alternate between active and waiting states without completing any tasks.

Answer

A condition where processes compete for shared resources, leading to reduced performance.

Question 10

Compare the features, advantages, and limitations of lock-based and semaphore-based concurrency control mechanisms. Discuss their suitability for different application types.

Accepted Answer

Lock-based: centralized control, mutual exclusion; Semaphore-based: decentralized control, resource counting.

Answer

Lock-based: decentralized control; Semaphore-based: centralized control.

Answer

Both lock-based and semaphore-based mechanisms are centralized in their control approach.

Answer

Lock-based mechanisms are ideal for small-scale applications, while semaphore-based mechanisms are more suited for large-scale, distributed systems.

Question 11

In distributed systems, which technique is NOT utilized for concurrency control?

Accepted Answer

Message Queues

Answer

Locks

Answer

Semaphores

Answer

Monitors

Question 12

Optimistic concurrency control assumes that:

Accepted Answer

Conflicts are infrequent and can be efficiently handled

Answer

Conflicts are common and should be prevented

Answer

Write operations are always serialized

Answer

Both reads and writes are always atomic

Question 13

What term describes a situation where multiple processes wait indefinitely for each other to release resources?

Accepted Answer

Deadlock

Answer

Starvation

Answer

Race condition

Answer

Livelock

Question 14

What is the fundamental difference between optimistic and pessimistic concurrency control approaches?

Accepted Answer

Optimistic concurrency control assumes no conflicts, while pessimistic concurrency control assumes conflicts.

Answer

Optimistic concurrency control detects conflicts, while pessimistic concurrency control prevents conflicts.

Answer

Optimistic concurrency control is more efficient, while pessimistic concurrency control is more reliable.

Answer

Optimistic concurrency control is used in distributed systems, while pessimistic concurrency control is used in centralized systems.

Question 15

Which benefit is associated with utilizing timestamps in concurrency control?

Accepted Answer

Improved performance

Answer

Reduced overhead

Answer

Increased reliability

Answer

Simplified implementation

Question 16

What is the primary objective of a transaction in a distributed system?

Accepted Answer

Guarantee atomicity, consistency, isolation, and durability (ACID) of data operations.

Answer

Enhance performance by batching operations.

Answer

Detect and recover from errors.

Answer

Manage concurrency and prevent deadlocks.

Question 17

What is the primary purpose of a semaphore in concurrency control?

Accepted Answer

To manage resource allocation

Answer

To enforce mutual exclusion

Answer

To detect and resolve deadlocks

Answer

To synchronize asynchronous events

Question 18

What is a primary challenge when using timestamps for concurrency control?

Accepted Answer

Timestamps require synchronized clocks across all system nodes

Answer

Timestamps may introduce precision errors

Answer

Timestamps cannot be used to order long-running transactions

Answer

Timestamps are unsuitable for environments with high contention

Question 19

What is the primary drawback of using locks for concurrency control?

Accepted Answer

Locks can cause processes to block indefinitely

Answer

Locks require complex coordination mechanisms

Answer

Locks are not applicable to distributed systems

Answer

Locks can lead to priority inversion

Question 20

Which benefit is associated with optimistic concurrency control?

Accepted Answer

It allows concurrent transactions to execute without blocking

Answer

It simplifies the detection and resolution of deadlocks

Answer

It ensures data integrity even in the event of system failures

Answer

It is suitable for systems with low contention

Question 21

What is the purpose of the two-phase commit protocol in distributed systems?

Accepted Answer

To ensure that database updates are committed or aborted atomically across all nodes

Answer

To prevent deadlocks during transaction execution

Answer

To improve the performance of database transactions

Answer

To handle replication of data across multiple nodes

Question 22

Which of the following is not a unique challenge in implementing concurrency control in distributed systems?

Accepted Answer

Absence of shared memory

Answer

Distributed nature of resources

Answer

Lack of centralized control

Answer

Non-determinism of network communication

Question 23

What is the primary goal of distributed deadlock detection?

Accepted Answer

To identify cycles in the dependency graph of blocked processes

Answer

To prevent deadlocks from occurring

Answer

To recover the system from deadlocks

Answer

To ensure that all processes in the system make progress

Question 24

Which of the following is NOT a type of lock used in concurrency control?

Accepted Answer

Optimistic lock

Answer

Exclusive lock

Answer

Shared lock

Answer

Read-write lock

Question 25

What is the key difference between blocking and non-blocking algorithms in concurrency control?

Accepted Answer

Blocking algorithms wait for a resource to become available while non-blocking algorithms do not

Answer

Non-blocking algorithms wait for a resource to become available while blocking algorithms do not

Answer

Blocking algorithms are more efficient than non-blocking algorithms

Answer

Non-blocking algorithms are more efficient than blocking algorithms

Question 26

What is the main objective of deadlock prevention in concurrency control?

Accepted Answer

To prevent deadlocks from occurring by avoiding unsafe states

Answer

To recover from deadlocks by detecting and breaking deadlock cycles

Answer

To detect deadlocks and notify the system administrator

Answer

To avoid deadlocks by using deadlock avoidance algorithms

Question 27

What is the primary responsibility of a distributed deadlock manager?

Accepted Answer

To detect and resolve deadlocks across multiple nodes in a distributed system

Answer

To prevent deadlocks from occurring in a distributed system

Answer

To recover from deadlocks by restarting affected transactions

Answer

To notify the system administrator about potential deadlocks

Question 28

When a transaction must pause to acquire a lock held by another transaction, which state does it enter?

Accepted Answer

Waiting state

Answer

Active state

Answer

Aborted state

Question 29

Which locking technique is used to prevent deadlocks by imposing a hierarchical order on locks?

Accepted Answer

Two-phase locking

Answer

Binary locks

Answer

Timestamp locks

Answer

Read-write locks

Question 30

Which of the following is an advantage of using semaphores for concurrency control?

Accepted Answer

Simplicity and ease of implementation

Answer

Deadlock avoidance

Answer

Improved performance in high-concurrency scenarios

Answer

Support for nested critical sections

Question 31

What is the key difference between a reader-writer lock and a mutex?

Accepted Answer

Reader-writer locks allow for concurrent access by multiple readers, while mutexes allow only exclusive access

Answer

Mutexes provide strong consistency guarantees, while reader-writer locks do not

Answer

Reader-writer locks are more efficient for read-intensive workloads, while mutexes are better for write-heavy scenarios

Answer

Mutexes are implemented using semaphores, while reader-writer locks are not

Question 32

Which scheduling algorithm is particularly well-suited for real-time systems?

Accepted Answer

Priority scheduling

Answer

First-come, first-served (FCFS)

Answer

Round-robin

Answer

Shortest remaining time first (SRTF)

Question 33

What is the primary goal of distributed mutual exclusion algorithms?

Accepted Answer

To ensure that multiple processes can access a shared resource without interference

Answer

To prevent deadlock situations in distributed systems

Answer

To guarantee the atomicity of transactions

Answer

To enhance the overall performance of distributed applications

Question 34

Which of the following is NOT a standard technique for concurrency control in distributed systems?

Accepted Answer

Transaction logs

Answer

Locks

Answer

Timestamps

Answer

Semaphores

Question 35

What is the primary purpose of a lock in the context of concurrency control?

Accepted Answer

To prevent concurrent access to a shared resource, ensuring data integrity and consistency.

Answer

To detect deadlocks

Answer

To coordinate access between threads

Answer

To store the state of a resource

Question 36

What is the primary purpose of timestamps in concurrency control?

Accepted Answer

To order concurrent transactions temporally, allowing for conflict detection and resolution.

Answer

To store transaction data

Answer

To detect deadlocks

Answer

To lock resources

Question 37

Describe the Two-Phase Locking (2PL) protocol in concurrency control.

Accepted Answer

A protocol that restricts transactions from acquiring and releasing locks in different phases, ensuring that all locks are acquired before any locks are released.

Answer

A protocol for detecting and resolving deadlocks

Question 38

What is the purpose of a deadlock detection algorithm in concurrency control?

Accepted Answer

To identify and resolve situations where multiple transactions are waiting for each other to release resources, preventing progress.

Answer

To prevent deadlocks from occurring

Question 39

Which of the following is NOT a common concurrency control mechanism?

Accepted Answer

Inheritance

Answer

Monitors

Answer

Locks

Answer

Semaphores

Question 40

In a distributed system, what is the primary function of a lock?

Accepted Answer

To prevent simultaneous access to a shared resource by multiple processes.

Answer

To enhance the speed of data access.

Answer

To track changes made to a shared resource.

Question 41

What is a key advantage of using semaphores for concurrency control?

Accepted Answer

They enable processes to communicate and synchronize access to shared resources.

Answer

They are simpler to implement compared to monitors.

Answer

They offer greater efficiency than locks.

Question 42

What is the primary difference between a lock and a monitor in the context of concurrency control?

Accepted Answer

Monitors provide advanced synchronization mechanisms, such as condition variables, while locks offer basic synchronization.

Answer

Locks are implemented in hardware, whereas monitors are software implementations.

Question 43

In a distributed system, what is a deadlock?

Accepted Answer

A situation where two or more processes are indefinitely waiting for each other to release a resource, leading to a system standstill.

Answer

A scenario where a process has acquired all the necessary resources.

Question 44

Which of the following techniques can help prevent deadlocks in a distributed system?

Accepted Answer

Timeout mechanisms

Answer

Priority inversion

Answer

Starvation

Answer

Resource hoarding

Question 45

What is the role of timestamps in optimistic concurrency control?

Accepted Answer

To detect and resolve conflicts that arise when multiple transactions attempt to modify the same data concurrently.

Answer

To prevent transactions from executing concurrently.

Question 46

What is a potential drawback of using a distributed database for concurrency control?

Accepted Answer

Increased network traffic and latency.

Answer

Improved data integrity.

Answer

Enhanced scalability.

Answer

Reduced system complexity.

Question 47

What is the primary goal of a distributed concurrency control algorithm?

Accepted Answer

To ensure that concurrent transactions execute as if they were executed sequentially.

Answer

To maximize the number of concurrent transactions.

Answer

To minimize the overhead of concurrency control.

Question 48

Which of the following accurately describes the primary benefit of using locks for concurrency control?

Accepted Answer

Ensures exclusive access to shared resources, preventing concurrent modifications by multiple threads or processes.

Answer

Guarantees deadlock-free execution, ensuring the system remains responsive

Answer

Improves performance in all cases, regardless of the workload and concurrency level

Answer

Eliminates the need for additional synchronization primitives, simplifying application development

Question 49

What is the primary disadvantage associated with using semaphores as a concurrency control mechanism?

Accepted Answer

Susceptible to priority inversion and starvation, where lower-priority threads can indefinitely delay higher-priority threads from acquiring resources.

Answer

Requires significant overhead and management, making them inefficient for managing large numbers of concurrent threads or processes

Answer

Not suitable for managing fine-grained concurrency, as they can lead to excessive resource contention and performance degradation

Answer

Difficult to implement in distributed systems due to the challenges of maintaining consistency across multiple nodes

Question 50

Which of the following characterizes optimistic concurrency control?

Accepted Answer

Validation of transactions occurs after their execution, allowing concurrent transactions to proceed without blocking until a conflict is detected.

Answer

Uses locking mechanisms to prevent conflicts, ensuring exclusive access to shared resources during transaction execution

Answer

Requires timestamps to identify conflicting operations, enabling the system to determine the order in which transactions should be executed

Answer

Guarantees serializability of transactions, ensuring that they appear to execute in a sequential order despite concurrent execution

Question 51

In timestamp-based concurrency control, what is the primary purpose of assigning timestamps to operations?

Accepted Answer

To establish a global ordering of operations, enabling the system to determine which operations conflict and should be aborted or retried

Answer

To prevent write-write conflicts by ensuring that only the most recent write operation is committed

Answer

To manage lock acquisition and release, ensuring that transactions acquire and release locks in a consistent order

Question 52

What is a common cause of deadlocks in distributed systems?

Accepted Answer

Circular wait for resources, where multiple processes or threads wait for each other to release resources, resulting in a system deadlock

Answer

Insufficient memory allocation, causing processes or threads to block while waiting for memory resources

Answer

Exceeding thread priority limits, leading to starvation of lower-priority threads and potential deadlocks

Answer

Lack of synchronization between threads, resulting in unpredictable execution order and potential race conditions

Question 53

What is the primary role of a distributed lock manager in a distributed system?

Accepted Answer

To coordinate the acquisition and release of locks across multiple nodes, ensuring consistent access to shared resources and preventing deadlocks

Answer

To maintain a central repository of shared resources, providing a single point of access for all nodes in the distributed system

Answer

To prevent deadlocks in distributed environments by detecting and resolving potential circular waits for resources

Question 54

Which technique is commonly employed to enhance the performance of two-phase locking?

Accepted Answer

Granularity reduction, which involves dividing locks into smaller units, allowing for finer-grained locking and reducing the likelihood of lock contention

Answer

Optimistic concurrency control, which allows concurrent transactions to proceed without blocking until a conflict is detected, improving performance in low-contention scenarios

Answer

Timestamp-based ordering, which assigns timestamps to operations to determine their execution order and resolve conflicts, improving performance in scenarios with high write concurrency

Answer

Deadlock detection and recovery, which involves identifying and resolving deadlocks when they occur, allowing the system to continue execution

Question 55

What is the fundamental difference between pessimistic and optimistic concurrency control?

Accepted Answer

Timing of conflict detection and resolution, with pessimistic concurrency control checking for conflicts before executing transactions and optimistic concurrency control checking after execution

Answer

Data consistency guarantees, with pessimistic concurrency control providing stronger guarantees than optimistic concurrency control

Answer

Transaction isolation levels, with pessimistic concurrency control typically supporting higher isolation levels than optimistic concurrency control

Answer

Use of locking mechanisms, with pessimistic concurrency control relying on locks and optimistic concurrency control using other mechanisms such as versioning

Question 56

What is a major challenge in implementing concurrency control in distributed systems?

Accepted Answer

Maintaining consistent global state, as updates to shared data by multiple nodes need to be propagated and synchronized across the distributed system to ensure data integrity and consistency

Answer

Transaction atomicity enforcement, as the distributed nature of the system can make it difficult to guarantee that all operations within a transaction are executed atomically

Answer

Deadlock avoidance, as the distributed nature of the system introduces additional complexity and potential for deadlocks

Answer

Resource starvation prevention, as the distributed system may have limited resources and managing resource allocation across multiple nodes can be challenging

Question 57

In the context of concurrency control, what is the primary objective of a distributed hash table (DHT)?

Accepted Answer

To facilitate efficient and scalable storage and retrieval of shared data across a distributed system, providing a consistent and reliable data store for concurrent access

Answer

To provide distributed lock management, ensuring exclusive access to shared resources and preventing deadlocks

Answer

To enable deadlock detection and recovery, identifying and resolving deadlocks that may occur in a distributed system