8 votes 8 votes Q.1 find total number of conflict serializable T1=R(A)W(A)R(B)W(B) T2=R(B)W(B)R(C)W(C) Q.2 find total number of conflict serializable for T1=R1(A)W1(A)R1(B)W1(B)R1(C)W1(C) T2=R2(A)W2(A)R2(B)W2(B)R2(C)W2(C). explanation??. Databases bad-question + – BASANT KUMAR asked Sep 27, 2018 BASANT KUMAR 4.2k views answer comment Share Follow See all 5 Comments See all 5 5 Comments reply Show 2 previous comments Shaik Masthan commented Sep 27, 2018 reply Follow Share https://gateoverflow.in/118640/gate2017-2-44 2 votes 2 votes Shaik Masthan commented Sep 27, 2018 reply Follow Share Actually, the answer provided in GATE-2017 question, didn't satisfy me. I did with my approach, you may check it. @BASANT KUMAR Don't add two different questions, in one post from next time. 0 votes 0 votes Shivani gaikawad commented Nov 1, 2018 reply Follow Share @shaikh thnxx ver much for uploading these images thesereally helped me 1 votes 1 votes Please log in or register to add a comment.
Best answer 17 votes 17 votes NEW APPROACH :- For question 1 :- see my answer at https://gateoverflow.in/118640/gate2017-2-44?show=289691#a289691 For question 2:- Before coming to question 2, please understand the procedure which is used in the Q1, due to it is same concept For clarity images :- https://drive.google.com/open?id=1dka-cqVm6ZppPI81Mm9WztqV_pG5iMMh Recommended to see the same type of question https://gateoverflow.in/272638/total-conflict-serializable-schedules OLD APPROACH :- For Question 1 :- For clarity images https://drive.google.com/open?id=1o12YFKd8JLhlXWLB1D3tuph91ENJ0OCd For Question 2 :- For Case 3 and Case 4 :- Note that R2(B) should be after W1(B) Shaik Masthan answered Sep 27, 2018 • selected Jan 24, 2019 by srestha Shaik Masthan comment Share Follow See all 34 Comments See all 34 34 Comments reply srestha commented Sep 28, 2018 reply Follow Share Can u give some good reference? I was getting some doubt 0 votes 0 votes Shaik Masthan commented Sep 28, 2018 reply Follow Share Mam, I don't have any reference 0 votes 0 votes srestha commented Sep 28, 2018 reply Follow Share So, from where u got the idea? 0 votes 0 votes Shaik Masthan commented Sep 29, 2018 reply Follow Share By practicing more problems (seeing different approaches by different people in different questions in GO ), I get this procedure. 0 votes 0 votes srestha commented Sep 30, 2018 reply Follow Share In question 1). why u not considering W(B) but why it has no conflict with R(A) and W(A) right? 0 votes 0 votes Shaik Masthan commented Oct 1, 2018 reply Follow Share in that case1 means, w2(B) come before r1(A) and w1(A) case 2 means, w2(B) comes after r1(A) and before w2(A) case 3 means, w2(B) comes after r1(A) and w1(A). 0 votes 0 votes srestha commented Oct 10, 2018 reply Follow Share @Shaik Here view equivalent schedule not possible rt? 0 votes 0 votes Shaik Masthan commented Oct 10, 2018 reply Follow Share they didn't mentioned any schedule, therefore the view equivalent question is invalid but we can find all the view equivalent schedules to T1 --> T2 or T2 --> T1 1 votes 1 votes Shivani gaikawad commented Oct 29, 2018 reply Follow Share @shaik masthan i understood the second part T2->T1(53) of first question but i am not getting T1->T2 of first question why there is only one possibility is it because in same schedule they should follow the same order but my doubt is that r(a) w(a) and r(b)w(b) is there one on data item a and other on b so cant they permute beacuse they are on reading and writing on different data item so how it will make difference in answer why cant they should be like these R(B)W(B)R(A)W(A)R(C)W(C)R(B)W(B) then we can get more possiblity please tell me where i am going wrong 0 votes 0 votes Shaik Masthan commented Oct 29, 2018 reply Follow Share why there is only one possibility is it because in same schedule they should follow the same order yes, with in a transaction you have to follow the order ===> after completing the operation R(B) it should go to W(B) then R(C) after that only W(C) 0 votes 0 votes Shivani gaikawad commented Nov 1, 2018 reply Follow Share Ok got it :) 0 votes 0 votes Nirmal Gaur commented Dec 6, 2018 reply Follow Share @ShaikMasthan Should we consider write-read conflicts only?? 0 votes 0 votes Shaik Masthan commented Dec 6, 2018 reply Follow Share Yes 0 votes 0 votes Nirmal Gaur commented Dec 6, 2018 reply Follow Share Why though? I mean why should'nt we consider write-write or read-write as they are also conflicting actions? 0 votes 0 votes Shaik Masthan commented Dec 7, 2018 reply Follow Share those are already taken care by w-r conflict itself. if in the question, it have only read in T1 and write in T2, then consider read-write conflict 0 votes 0 votes Nirmal Gaur commented Dec 7, 2018 reply Follow Share So while finding schedules conflict equivalent to T1 → T2, for any data item Q, we need to find the first action on Q by T2 that conflicts with any of the action on Q by T1 and that would cover up all the remaining conflict. Am I getting it right? 1 votes 1 votes Shaik Masthan commented Dec 7, 2018 reply Follow Share on each data item... 0 votes 0 votes Nirmal Gaur commented Dec 7, 2018 reply Follow Share Yes for each data item Q.. Am i thinking it right? 0 votes 0 votes Satbir commented Dec 20, 2018 reply Follow Share Gr8 explanation. It took 15 mins to understand from your explanation.I am just thinking how would i solve such questions in xam. 0 votes 0 votes Shaik Masthan commented Dec 20, 2018 reply Follow Share if you understood the method, and practice enough, with in 5 min you can do it ! By the way, 2$^{nd}$ question can't give in GATE, they give only small problem which can we do with in 5 min. 1 votes 1 votes Shaik Masthan commented Jan 5, 2019 reply Follow Share i added one more approach to solve this type of questions with in less time with some more preciously. i recommended You to check it ! 0 votes 0 votes MiNiPanda commented Jan 10, 2019 reply Follow Share @Shaik Masthan Can you please explain the solution to the 2nd question a bit? I am not getting the cases..The way I solved is giving me more no. of schedules.. 0 votes 0 votes Shaik Masthan commented Jan 11, 2019 reply Follow Share new approach or old approach ? if you doesn't get old approach is, there is no problem new approach is very easy and less time consume and no need to bother about intersection cases ! 0 votes 0 votes MiNiPanda commented Jan 11, 2019 reply Follow Share You solved the 2nd question in one method only right? 0 votes 0 votes Shaik Masthan commented Jan 11, 2019 reply Follow Share No, i solved 2nd question in two approaches ! infact 1st question new approach kept in some other question 0 votes 0 votes Magma commented Jan 18, 2019 reply Follow Share @Shaik Masthan why you only take Write - Read conflict here By draw topological diag it's very easy to solve but I didn't understand that how you made it acc to question 2 This topology is correct ??? but acc to this topology "correct answer is not coming :/ " 0 votes 0 votes Shaik Masthan commented Jan 18, 2019 reply Follow Share why you only take Write - Read conflict here that is DAG, So excess links removed ! if you didn't get it, just assume, 3 --> 6 you drawn a link. Then think 6 should be after 3 and 4, and 4 should be after 3 ==> you must have to do 3--> 4--->6 Your DAG, representating T1 --> T2 0 votes 0 votes Magma commented Jan 18, 2019 reply Follow Share Then in this case answer is not coming right only one arrangement is possible you see 1 -->2 ---> 3--->4---->6---->7--->8--->9 :/ 0 votes 0 votes Shaik Masthan commented Jan 18, 2019 reply Follow Share you calculated upto T1 --> T2 part Now calculate T2 --> T1 part then add both of them for DAG approach, Question1 kept on another link, ( which is at GATE question ) Question 2 is only present here 0 votes 0 votes Magma commented Jan 18, 2019 reply Follow Share I'm talking about Question no 1 ) 0 votes 0 votes Shaik Masthan commented Jan 18, 2019 reply Follow Share @magma is question no.1 present in this answer ( DAG approach ) ? 0 votes 0 votes Magma commented Jan 18, 2019 reply Follow Share No it's not present But we can use this DAG approach in similar type of questions where we have to find no of conflict serializable right ? 0 votes 0 votes Ashwani Yadav commented Jan 22, 2019 reply Follow Share thanks :) 0 votes 0 votes vishnu_m7 commented Sep 20, 2020 reply Follow Share @Shaik Masthan In the first method, second image – https://drive.google.com/file/d/1Z-tlThOEyVlBjV8Zky5_Wc3z7L-hvSGc/view?usp=sharing Total number of possibilities such that T2->T1 = T1->T2 = 56 is because of the symmetricity of the DAG, right? i.e if we draw the graph for T2->T1 it will be same as that of T1->T2 with the corresponding labels interchanged(G for A, H for B etc) , right? 0 votes 0 votes Please log in or register to add a comment.