Ch 44: Concurrency Control in Databases

In-depth analysis of concurrent execution hazards, conflict equivalent schedules, testing serializability via precedence graphs (serialization graphs), and cycles.

7 Questions7 MCQs0 Short Questions0 Long Questions

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CS403 - Database Management Systems Examination Practice

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❓ MCQ📘 CS403📑 Lec 44🏷️ 44.4. Serializability and Conflict SerializabilityMedium🔁⭐💡🌟📄🎓VU🏛️VU

In transaction management, serializability is the criteria for correctness in interleaved transaction execution. Does an interleaved (concurrent) schedule of transactions always create serialized groups, and what does serializability guarantee?

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Serial Schedule: T1 -> T2 (No Interleaving)
Interleaved Schedule: R1(A), R2(A), W1(A), W2(A) (Interleaved operations)

A.No, interleaved schedules do not automatically form serial groups, but serializability ensures the final database state is equivalent to executing the transactions sequentially (serially) without interleaving.
B.Yes, interleaved schedules always group transactions into strict serial blocks that block other transactions from executing.
C.No, interleaved schedules must execute in a randomized, unpredictable order, and serializability guarantees that transactions will always fail with a deadlock.
D.Yes, serializability guarantees that all transaction data is permanently kept in volatile memory buffers to optimize read speed.

❓ MCQ📘 CS403📑 Lec 44🏷️ 44.4. Deadlock Prevention and DetectionMedium🔁⭐💡🌟📄🎓VU🏛️VU

Which of the following describes a dynamic, timestamp-based deadlock prevention protocol where an older transaction (with a smaller timestamp) is allowed to wait for a lock held by a younger transaction, but a younger transaction immediately rolls back ('dies') if it requests a lock held by an older transaction?

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IF Timestamp(Ti) < Timestamp(Tj) THEN Ti WAITS; 
ELSE Ti DIES; -- Wait-Die Scheme

A.The Wait-Die Scheme
B.The Wound-Wait Scheme
C.The Optimistic Concurrency Protocol
D.The Two-Phase Locking (2PL) Protocol

❓ MCQ📘 CS403📑 Lec 44🏷️ 44.1. Problems of Concurrent ExecutionHard🔁⭐💡🌟📄🎓VU🏛️VU

In a multi-user DBMS environment, which of the following lists represents the three primary concurrency problems that occur when multiple transactions access and modify the same data objects concurrently?

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-- Example scenario demonstrating Lost Update:
-- T1: Read(BAL) -> BAL = BAL - 50 -> Write(BAL)
-- T2: Read(BAL) -> BAL = BAL + 10 -> Write(BAL) [Overwrites T1]

A.Lost Update Problem, Temporary Update (Dirty Read) Problem, and Inconsistent Analysis Problem
B.Functional Dependency, Multi-valued Dependency, and Join Dependency
C.Volatile Loss, Non-volatile Log Failure, and Transaction Rollback
D.Deadlock, Starvation, and Locking Overhead

📝 Short Q📘 CS403📑 Lec 44🏷️ 44.4. Deadlock Prevention and DetectionHard🔁⭐💡🌟📄🎓VU🏛️VU

Explain how the timestamping approach works in concurrency control to prioritize transactions and maintain serializability without utilizing physical locks.

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-- Wait-Die Protocol Rule:
-- If TS(Ti) < TS(Tj) then Ti waits;
-- Else Ti dies (rolls back).

🧠 Long Problem📘 CS403📑 Lec 44🏷️ 44.4. Deadlock Prevention and DetectionHard🔁⭐💡🌟📄🎓VU🏛️VU

During concurrent database transaction management, deadlocks represent a circular wait state. Write down the four fundamental steps required to perform deadlock resolution in a database management system.

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-- Deadlock Cycle Detection in Wait-For Graph (WFG):
-- T1 waits for T2, T2 waits for T1 ---> Deadlock Detected

📝 Short Q📘 CS403📑 Lec 44🏷️ 44.3. Lock Manager and Concurrency ControlMedium🔁⭐💡🌟📄🎓VU🏛️VU

Name and briefly describe the two primary locking modes managed by the Database Concurrency Control lock manager to coordinate multi-user data access.

❓ MCQ📘 CS403📑 Lec 44🏷️ 44.5. Introduction to LockingMedium🔁⭐💡📄🎓VU🏛️VU

True or False: Under the Two-Phase Locking (2PL) protocol, once a transaction releases a lock, it may acquire additional locks as needed.

A.True
B.False

Ch 44: Concurrency Control in Databases

CS403 - Database Management Systems Examination Practice

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CS403 - Database Management Systems Examination Practice

Mid Term Examination

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