Which of the following scenarios may lead to an irrecoverable error in a…
20032025
Which of the following scenarios may lead to an irrecoverable error in a database system ?
- A.
A transaction writes a data item after it is read by an uncommitted transaction
- B.
A transaction reads a data item after it is read by an uncommitted transaction
- C.
A transaction reads a data item after it is written by a committed transaction
- D.
A transaction reads a data item after it is written by an uncommitted transaction
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Correct answer: D
Irrecoverable errors in a database system occur when the system cannot restore consistency after a failure. Two common scenarios are dirty writes and dirty reads.
A dirty write happens when a transaction writes to a data item that was previously read by an uncommitted transaction. If the reading transaction rolls back, the written data may be inconsistent, and the system cannot recover the original state.
A dirty read occurs when a transaction reads data written by an uncommitted transaction. If the writing transaction rolls back, the reading transaction has used invalid data, leading to potential irrecoverable inconsistencies.
In both cases, the system may not be able to roll back the operations safely, making the error irrecoverable.
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