This is the DBMS questions and answers section on "Deadlocks" with explanation for various interview, competitive examination and entrance test. Solved examples with detailed answer description, explanation are given and it would be easy to understand.
1. A system is in a ______ state if there exists a set of transactions such that every transaction in the set is waiting for another transaction in the set.
Answer: Option C
Explanation:
Deadlock
When one data item is waiting for another data item in a transaction then system is in deadlock.
2. The deadlock state can be changed back to stable state by using _____________ statement.
- A. Commit
- B. Rollback
- C. Savepoint
- D. Deadlock
Answer: Option B
Explanation:
Rollback
Rollback is used to rollback to the point before lock is obtained.
3. What are the ways of dealing with deadlock ?
- A. Deadlock prevention
- B. Deadlock recovery
- C. Deadlock detection
- D. All of the mentioned
Answer: Option D
Explanation:
All of the mentioned
Deadlock prevention is also called as deadlock recovery.Prevention is commonly used if the probability that the system would enter a deadlock state is relatively high; otherwise, detection and recovery are more efficient.
4. When transaction Ti requests a data item currently held by Tj , Ti is allowed to wait only if it has a timestamp smaller than that of Tj (that is, Ti is older than Tj ). Otherwise, Ti is rolled back (dies). This is
- A. Wait-die
- B. Wait-wound
- C. Wound-wait
- D. Wait
Answer: Option A
Explanation:
Wait-die
The wait–die scheme is a non-preemptive technique.
5. When transaction Ti requests a data item currently held by Tj , Ti is allowed to wait only if it has a timestamp larger than that of Tj (that is, Ti is younger than Tj ). Otherwise, Tj is rolled back (Tj is wounded by Ti ). This is
- A. Wait-die
- B. Wait-wound
- C. Wound-wait
- D. Wait
Answer: Option C
Explanation:
Wound-wait
The wound–wait scheme is a preemptive technique. It is a counterpart to the wait–die scheme.
