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DBMS Log-Based Recovery MCQs

DBMS Log-Based Recovery MCQs: This section contains multiple-choice questions and answers on Log-Based Recovery in DBMS.
Submitted by Anushree Goswami, on April 18, 2022

1. Logs consist of a ___ of records.

  1. Compilations
  2. Series
  3. Data
  4. Table

Answer: B) Series

Explanation:

Logs consist of a series of records.

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2. In case of any failure, a log of each transaction can be recovered there from some ___ storage.

  1. Stable
  2. Unstable
  3. Recovery
  4. System

Answer: A) Stable

Explanation:

In case of any failure, a log of each transaction can be recovered there from some stable storage.

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3. ___ is used to keep track of all database operations.

  1. Dragging
  2. Logging
  3. Receiving
  4. Recovery

Answer: B) Logging

Explanation:

Logging is used to keep track of all database operations.

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4. It is advisable, to store the ___ before applying the actual transaction to the database.

  1. Data
  2. Logs
  3. Receive
  4. Record

Answer: B) Logs

Explanation:

It is advisable, however, to store the logs before applying the actual transaction to the database.

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5. How many approaches are there to modify the database?

  1. 2
  2. 3
  3. 4
  4. 5

Answer: A) 2

Explanation:

2 approaches are there to modify the database.

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6. What are the two approaches to modify the database?

  1. Deferred database modification
  2. Immediate database modification
  3. Both A and B
  4. None of the above

Answer: C) Both A and B

Explanation:

Two approaches to modify the database are -

  1. Deferred database modification
  2. Immediate database modification

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7. When ___ modification is applied, the change to the database does not occur until the transaction is committed.

  1. Deferred
  2. Immediate
  3. Both A and B
  4. None of the above

Answer: A) Deferred

Explanation:

When deferred modification is applied, the change to the database does not occur until the transaction is committed.

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8. All logs are created and stored in ___ storage when the deferred database method is used, and data is synced to the database when a transaction commits.

  1. Stable
  2. Unstable
  3. System
  4. Recovery

Answer: A) Stable

Explanation:

All logs are created and stored in stable storage when the deferred database method is used, and data is synced to the database when a transaction commits.

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9. Modifications to the database occur while a transaction is still active, using the ___ modification technique.

  1. Deferred
  2. Immediate
  3. Both A and B
  4. None of the above

Answer: B) Immediate

Explanation:

Modifications to the database occur while a transaction is still active, using the Immediate modification technique.

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10. The ___ is updated immediately after every operation when using the immediate modification technique.

  1. Table
  2. Row
  3. Column
  4. Database

Answer: D) Database

Explanation:

The database is updated immediately after every operation when using the immediate modification technique.

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11. Once the system crashes, the log is consulted to determine what needs to be un___ and what needs to be re-___.

  1. Open
  2. Tie
  3. Done
  4. Wrap

Answer: C) Done

Explanation:

Once the system crashes, the log is consulted to determine what needs to be undone and what needs to be re-done.

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12. Log records that contain the records <__, Start> and <__, Commit> or <__, Commit> indicate that the Transaction __ must be rewritten.

  1. Start
  2. Commit
  3. Ti
  4. None

Answer: C) Ti

Explanation:

Log records that contain the records <Ti, Start> and <Ti, Commit> or <Ti, Commit> indicate that the Transaction Ti must be rewritten.

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13. The Transaction Ti needs to be reversed if the log consists of record <Tn, Begin>, but does not contain record <Ti, Commit> or <Ti, ____>.

  1. Begin
  2. End
  3. Commit
  4. Abort

Answer: D) Abort

Explanation:

The Transaction Ti needs to be reversed if the log consists of record <Tn, Begin>, but does not contain record <Ti, Commit> or <Ti, Abort>.

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