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+26 votes
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Which of the following scenarios may lead to an irrecoverable error in a database system?

  1. A transaction writes a data item after it is read by an uncommitted transaction
  2. A transaction reads a data item after it is read by an uncommitted transaction
  3. A transaction reads a data item after it is written by a committed transaction
  4. A transaction reads a data item after it is written by an uncommitted transaction
asked in Databases by Veteran (59.5k points) | 2.9k views
0
APPROPIATE ANSWER IS D
+1
  1. A transaction writes a data item after it is read by an uncommitted transaction 

 Blind Write. So commit or not, does not matter.

0
Thanks man :-)

You only made the point clear

5 Answers

+27 votes
Best answer
D) This is dirty read. In case if transaction reading uncommited data commits, irrecoverable error occurs of uncommited transaction fails. So D is answer

B) This is non issue.Both transaction reading data.

C) This is non issue.

A) Here if transaction writing data commits , then transaction which read the data might get phantom tuple/ Unrepeatable error. Though there is no irrecoverable error possible even in this option.
answered by Boss (42.6k points)
selected by
+7 votes
D. If Data is uncommitted , then transactions reads a data after write always give error.
answered by Active (1.6k points)
+3 votes
D

Option C is a normal operation. Option B is also fine as no write operation is involved. Option A can be recovered, but option D can't be.
answered by Junior (689 points)
–1
after write by uncommited transaction again write is a problem.

but after write by uncommited transaction then read why it will be problem?
–2 votes
APPROPIATE ANSWER IS D
answered by Junior (609 points)
0
cn u explain this by easy example?
–2 votes

ANS ---     Option D

answered by (429 points)
Answer:

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