Problem 2 Consider a database with tables R1(A) and R2(B) and transaction T1: T1

Question

Problem 2 Consider a database with tables R1(A) and R2(B) and transaction T1: T1: set transaction isolation level repeatable read; Select from R1 Select from R1 Select * from R2 Suppose table R1 initially has one tuple with value A-3 and table R2 initially has one tuple with value B-6. Consider the following possible transactions T2, executed around the same time as T1. Which one of them can cause the two transactions to exhibit nonserializable behavior? a) T2: set transaction serializable; update R1 set A-4; delete from R2 where B-6; commit; b) T2: set transaction serializable; delete from R2; insert into R2 values (6); commit; c) T2: set transaction serializable; update R2 set B-7; commit; d) T2: set transaction serializable; insert into R2 values (5); delete from R1 where A-2; commit;

Explanation / Answer

Solution:

a)

Explanation:

Because in this part there is a read-write problem and the topological graph will have a cycle for this transaction.

Which means non-serializable

d)

Explanation:

Same goes here the topological graph will have cyclic nature which means non-serializable.

because before R1 insert is committed R2 is deleting the tuple. lost update problem

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