Transaction 1

Question

How many concurrent schedules are conflict serializable of given transactions T₁ and T₂:

Answer 1

• Only 2 conflict serial schedule is possible.

• From Transaction T1---->T2 . Only one conflict schedule is possible . We can not swap any data item . When we swap then it create a cycle. 

• Similarlly for T2------->T1

Comments

Sir one doubt question says about concurrent schedules which are conflict serializable. You took two transaction and applied them serially. You could have interleaved them. By doing so will it create any different answer ?

My doubt is sir, Schedule means exact sequence of transaction order to be followed since here there were only two transaction so it could be either of T1 --> T2 or vice versa, Say for example sir we had given the same question with three transaction then how would you deal that question.

I guess you will try to find out the serial schedule if possible like:-

T1-->T2-->T3

      or

T2-->T1-->T3

 likewise total 6 combination and we will check which are possible by doing different interleaving of the operation.

Am i right sir?

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Yea you are right.

For three transaction .Question become complex.

Answer 2

Only two. Either complete T1 then complete T2 or complete T2 then complete T1. Any other schedule won't be conflict serializable.

Comments

Sir plz tell the approach how u figured out the answer

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Because conflict pairs order can't be changed ,since two conflict pairs are in T1 ,order can be changed and Same for T2. So either you have to execute T1 first then T2 or vice versa.