TestBook Test Series Database

Question

Q 40). Which of the following is/are TRUE?

I). Strict schedule is a cascade-less schedule and recoverable schedule.

II). Every cascade-less schedule is recoverable schedule.

III). Every conflict serializable schedule is recoverable.

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 $I \ and \ II \ only$

 $II \ and \ III \ only$

 $I \ and \ III \ only$

Please answer with reference why III is false.

I see venn diagram -> https://en.wikipedia.org/wiki/Schedule_%28computer_science%29#Hierarchical_relationship_between_serializability_classes

Here. (Same is used in ans key, but no reference for it !)

Comments

strict schedule =CLR+no lostupdate problem

cascadeless schedule =recoverable + no cascading roll backs
eveery CSS is VSS
but how every css is recoverable.??

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Every Cascade less schedule is recoverable 

since in cascade less we have both read and write operations after 1st updation where as in recoverable we have only read operations after 1st updation

Answer 1

In the venn diagram , it is clear that conflict serializable is not a subset of recoverable schedule so (III) can be false.