Queue of entering processes Monitor waiting area Entrance MONITOR Local data Condition el Cwait(cl) Condition variables Procedure I Condition cn Cwait (en) Procedure k Urgent queue csignal Initialization code 미머 Exit Figure 3. The structure of a monitor relative to concurrency. Questions: 5. Deduce at least one (1) characteristic of a monitor based on Figure 3. Elaborate on your answer. 6. Would you agree that a monitor, as a concurrency mechanism, can support process synchronization? Why or why not?

Queue of entering processes Monitor waiting area Entrance MONITOR Local data Condition el Cwait(cl) Condition variables Procedure I Condition cn Cwait (en) Procedure k Urgent queue csignal Initialization code 미머 Exit Figure 3. The structure of a monitor relative to concurrency. Questions: 5. Deduce at least one (1) characteristic of a monitor based on Figure 3. Elaborate on your answer. 6. Would you agree that a monitor, as a concurrency mechanism, can support process synchronization? Why or why not?

Database System Concepts

7th Edition

ISBN:9780078022159

Author:Abraham Silberschatz Professor, Henry F. Korth, S. Sudarshan

Publisher:Abraham Silberschatz Professor, Henry F. Korth, S. Sudarshan

Chapter1: Introduction

Section: Chapter Questions

Problem 1PE

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Write short notes on, (а) Optimistic concurrency control (b) Phantom deadlock.
Describe how "optimistic concurrency control" works in transaction processing.
Part IlII: Monitor Queue of entering processes Monitor waiting area Entrance 미머 MONITOR Local data Condition el Cwait(cl) Condition variables Procedure 1 Condition cn Cwait (cn) Procedure k Urgent queue csignal Initialization code 미머 Exit Figure 3. The structure of a monitor relative to concurrency. Questions: 5. Deduce at least one (1) characteristic of a monitor based on Figure 3. Elaborate on your answer. 6. Would you agree that a monitor, as a concurrency mechanism, can support process synchronization? Why or why not?
Which concurrency mechanism would you suggest that might prevent the deadlock situation above? Rationalize answer. Do Execution Paths 3 and 4 encompass the first three conditions for a deadlock to occur? Explain your answer.
What is the appeal of optimistic concurrency control approaches? Why might optimistic concurrency control approaches not be used even if they provide better expected performance?
Describe the three most common problems with concurrent transaction execution.Explain how concurrency control can be used to avoid those problems.
Many applications need to generate sequence numbers for each transaction. a. If a sequence counter is locked in two-phase manner, it can become a concurrency bottleneck. Explain why this may be the case. b. Many database systems support built-in sequence counters that are not locked in two-phase manner; when a transaction requests a sequence number, the counter is locked, incremented and unlocked. i. Explain how such counters can improve concurrency. ii. Explain why there may be gaps in the sequence numbers belonging to the final set of committed transactions.
Just like in other distributed systems, concurrency control is an issue in Distributed Database Systems. In a setup where fragments are NOT replicated, would there be a need to enforce concurrency control measures such as 2PL(Two-phase locking)? Explain.
When an optimistic approach to concurrency management is used, transactions often take a very lengthy time to complete. Explain.
Explain the concept of distributed concurrency control and compare different concurrency control protocols.
A transaction's processing time may be slowed when using optimistic concurrency control. Explain?
Describe the concept of deadlock in the context of concurrency control. How can it be prevented or resolved?