Test by Bikram | Mock GATE | Test 1 | Question: 25

Question

Which of the following is true?

1.    Blind writes appear in any view serializable schedule that is not conflict serializable.
2.    Blind writes appear in some view serializable schedule that is also conflict serializable.
3.    Blind writes appear in all view seriallzable schedules that are also conflict serializable.
4.    Blind writes appear only in conflict serializable schedule that is not view serializable.

• A. II and III
• B. II and IV
• C. I only
• D. I and II

Answer 1

" Any view serializable schedule that is not conflict serializable must contain a blind write." 

But presence of blind write doesnt mean that a given view serializable schedule is not conflict serializable. i.e., there are view serializable schedules with blind writes that are

1. conflict serializable
2. non conflict-serializable

see this https://en.wikipedia.org/wiki/Blind_write

Answer 2

Correct answer should be option a.

Comments

@Bikram sir, you trapped me with sequence of option given  I marked in hurry just looking by option "D" but option "D" was for statement 1

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and even, with blind writes it not necessarily View serializable, it is necessary condition but not sufficient

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can someone give example to prove that point