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Chapter 19: Problem 27

What implications would a no-steal/force buffer management policy have on checkpointing and recovery?

Short Answer

Expert verified
A no-steal/force buffer management policy implies that uncommitted data from an incomplete transaction cannot overwrite the committed data on disk, ensuring the atomicity and isolation of transactions. This simplifies recovery as there's no need to 'undo' unwritten changes of uncommitted transaction after a system failure. At the same time, the force policy that requires all the associated data to be written back to the disk once a transaction is completed ensures the durability of transactions. However, this might need more time due to the forced disk writes for every transaction commit, but could make checkpointing more efficient.

Step by step solution

01

Understand Buffer Management Policy

A 'no-steal/force' buffer management policy means that uncommitted data is not written to disk ('no-steal') and all modified buffers are forced out to disk when a transaction finishes ('force').
02

Understand Checkpointing and Recovery

Checkpointing refers to the process of saving the state of the system at specific points, known as checkpoints. In the context of a database, it means recording the state of a transaction at a certain point so that changes can be efficiently rolled back in case of a system failure. Recovery, on the other hand, refers to the process of returning the database to a consistent state after some sort of failure.
03

Implications of No-Steal on Checkpointing and Recovery

With the no-steal policy, uncommitted data is not allowed to be written back to disk from the buffer. This policy helps to preserve atomicity and isolation of transactions because uncommitted data from an incomplete transaction cannot overwrite the committed data on disk. This makes recovery simpler as there's no need to undo unwritten changes of uncommitted transaction on a system failure.
04

Implications of Force on Checkpointing and Recovery

With the force policy, when a transaction is completed, all the associated data in the buffer must be immediately written back to the disk. This ensures durability of transactions because once a transaction is committed, even if there occurs a system failure, the changes made by the transaction are safely stored on the disk. So, it simplifies recovery as there would be no need to redo committed transactions since all changes of a committed transaction are forced to write to disk before it commits. This can make checkpointing more efficient, but might require more time due to the forced disk writes for every transaction commit.

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Most popular questions from this chapter

Discuss the different types of transaction failures. What is meant by catastrophic failure?

Choose the correct answer for each of the following multiple-choice questions:Incremental logging with deferred updates implies that the recovery system must necessarily a. store the old value of the updated item in the log. b. store the new value of the updated item in the log. c. store both the old and new value of the updated item in the log. d. store only the Begin Transaction and Commit Transaction records in the log.

Choose the correct answer for each of the following multiple-choice questions: When a failure occurs, the log is consulted and each operation is either undone or redone. This is a problem because a. searching the entire log is time consuming. b. many redo's are unnecessary. c. both (a) and (b). d. none of the above.

Choose the correct answer for each of the following multiple-choice questions: The write ahead logging (WAL) protocol simply means that a. the writing of a data item should be done ahead of any logging operation. b. the log record for an operation should be written before the actual data is written. c. all log records should be written before a new transaction begins execution. d. the log never needs to be written to disk.

What are log sequence numbers (LSNs) in ARIES? How are they used? What information does the Dirty Page Table and Transaction Table contain? Describe how fuzzy checkpointing is used in ARIES.
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