18 Questions
What happens to a transaction when it enters the failed state in a database system?
It is rolled back and enters the aborted state.
Under what circumstances can a failed transaction be restarted in a database system?
If the failure was due to a hardware or software error not created through the internal logic of the transaction.
Why might a database system decide to kill a transaction?
Due to internal logical errors that require rewriting the application program.
Why is it essential to be cautious when dealing with observable external writes in a database system?
Because such writes cannot be erased once they have occurred.
What does it mean for a transaction to be considered a new transaction when restarted in a database system?
It starts its execution from scratch with new attributes and operations.
Why do most systems allow observable external writes only after a transaction has entered the committed state?
To avoid exposing partial or inconsistent data to users or external systems.
What property in databases ensures that transactions either fully complete or have no effect at all?
Atomicity
Which property refers to the requirement that transactions must operate independently without interference from other concurrently executing database statements?
Isolation
What property ensures that transactions persist across system crashes in databases?
Durability
In database systems, which property is violated if a system 'forgets' about a transaction after a crash?
Durability
What is the term used to describe the 'all-or-none' property in databases which guarantees that transactions are indivisible?
Atomicity
Which database property ensures that transactions execute without interference from other concurrent operations?
Isolation
What happens if the system fails after a transaction has entered the committed state but before completing external writes?
The database system will carry out the external writes when the system is restarted.
What is a possible issue when handling external writes for dispensing cash at an automated teller machine?
Dispensing cash when the user is present.
What action needs to be taken if the database system crashes just after a booking transaction commits over the Web?
Executing a compensating transaction upon system restart.
How is atomicity in databases related to handling system failures?
Atomicity guarantees that either all operations of a transaction are carried out or none are.
Why is it important for applications to be designed such that users can verify the success of their transactions after a system failure?
To ensure users know whether they have to redo their transactions.
In the context of database recovery systems, what does durability refer to?
Ensuring that all committed transactions persist through failures.
Explore techniques for dealing with data loss on disk as discussed in Chapter 16. Learn about transactions entering a failed state, being rolled back to an aborted state, and the options available for restarting them after errors.
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