0 votes 0 votes Is the following schedule conflict serializable T1 T2 T3 W(X) commit R(X) W(X) R(X) W(X) commit W(X) commit Databases transaction-and-concurrency databases + – jatin khachane 1 asked Jan 16, 2019 jatin khachane 1 1.3k views answer comment Share Follow See all 26 Comments See all 26 26 Comments reply Manas Mishra commented Jan 16, 2019 reply Follow Share yes becoz after t3 commit t2's write came 1 votes 1 votes jatin khachane 1 commented Jan 16, 2019 reply Follow Share does commit matters while checking serializability @Shaik Masthan @Mk Utkarsh 0 votes 0 votes Mk Utkarsh commented Jan 16, 2019 reply Follow Share Manas Mishra Answer here is wrong? 0 votes 0 votes jatin khachane 1 commented Jan 16, 2019 reply Follow Share https://gateoverflow.in/112238/self-doubt check this one also ..answer by bikram sir 0 votes 0 votes Manas Mishra commented Jan 16, 2019 reply Follow Share might be i m wrong , so then is it not serializable ? 0 votes 0 votes Satbir commented Jan 16, 2019 reply Follow Share YES. It is not a recoverable schedule but it is conflict serializeable schedule. we don't compare after commit operation. Like R3(X) W3(X) will not be compared to the second W2(X) because T3 is committed and is no more present in the system. 0 votes 0 votes jatin khachane 1 commented Jan 16, 2019 reply Follow Share According to navathe book def of conflict operations definition: it dosn’t say anything about commit of transactions 0 votes 0 votes Satbir commented Jan 16, 2019 reply Follow Share https://gateoverflow.in/1988/gate2014-2-29 0 votes 0 votes Mk Utkarsh commented Jan 16, 2019 reply Follow Share Satbir what about it? 0 votes 0 votes jatin khachane 1 commented Jan 16, 2019 reply Follow Share @Shaik Masthan It will be helpful if you explain are answers in this links wrong ? https://gateoverflow.in/81125/conflict-serializability-when-schedule-contains-commit https://gateoverflow.in/112238/self-doubt 0 votes 0 votes Satbir commented Jan 16, 2019 reply Follow Share @Mk Utkarsh read the comments in that question. The concept used here is similar to the question mentioned. one of the comment is Wiki says:->>Another definition for conflict-serializability is that a schedule is conflict-serializable if and only if its precedence graph/serializability graph, when only committed transactions are considered, is acyclic (if the graph is defined to include also uncommitted transactions, then cycles involving uncommitted transactions may occur without conflict serializability violation). 0 votes 0 votes Mk Utkarsh commented Jan 16, 2019 reply Follow Share Satbir yes that means transactions containing abort are ignored 0 votes 0 votes srestha commented Jan 16, 2019 reply Follow Share it will not conflict serializable https://gateoverflow.in/266549/raghuramkrishnan 0 votes 0 votes Satbir commented Jan 16, 2019 reply Follow Share @srestha the question which you have mentioned is having commit and abort operations at the end. first cycle is forming and then commit and abort are taking place. but in this question cycle is not forming between T2 and T3 because of the commit operation of T3. Can you please explain or give reference why we don't see commit operation in case of conflict serializability ? 0 votes 0 votes jatin khachane 1 commented Jan 17, 2019 reply Follow Share @Arjun sir, it will be hepful if you clarify this ..lot of confusion :( 0 votes 0 votes Shaik Masthan commented Jan 17, 2019 reply Follow Share As per my knowledge, COMMIT means, that transaction completes, then how can it will be conflict with others after it's commit ? I read that ( From NPTEL lectures ) , there are some irrecoverable schedules which are serializable. This question is the example for that type ! 3 votes 3 votes Satbir commented Jan 17, 2019 reply Follow Share Yes ...correct @Shaik Masthan 0 votes 0 votes Mk Utkarsh commented Jan 17, 2019 reply Follow Share Shaik Masthan link of that NPTEL lecture? 0 votes 0 votes akash.dinkar12 commented Jan 17, 2019 reply Follow Share @Shaik Masthan where did u read this?? I read that ( From NPTEL lectures ) , there are some irrecoverable schedules which are serializable. 0 votes 0 votes Shaik Masthan commented Jan 17, 2019 reply Follow Share At 19:00 1 votes 1 votes Mk Utkarsh commented Jan 17, 2019 reply Follow Share T1 T2 R(x) W(x) R(x) W(x) Commit Commit This is irrecoverable but conflict serializable but we are discussing something else na 2 votes 2 votes muthu kumar commented Jan 17, 2019 reply Follow Share Bro, If conflict serializable then we can give the order.. like T1->T2->T3 but it is conflicting. T1->T2->T3 and this is also conflicting. then what is the effect of considering commit in this?? 0 votes 0 votes Shaik Masthan commented Jan 17, 2019 reply Follow Share if it is View serializable, then exactly we can't give some order, right ? even in Thomos write Rule, we ignore obsolate writes, right ? @Mk Utkarsh That's why i specified as per my knowledge :) Then how this gate question is serializable ? https://gateoverflow.in/1988/gate2014-2-29 0 votes 0 votes Mk Utkarsh commented Jan 17, 2019 reply Follow Share Because no cycle 2 votes 2 votes susgir2 commented Jan 17, 2019 reply Follow Share Correct me if I am wrong. @Shaik Masthan @Mk Utkarsh the schedule is not C.S as we have a cycle in it(T2 , T3).. Commits dont' matter. only aborts do as we don't count them while makeing dependency graph. 0 votes 0 votes jatin khachane 1 commented Jan 17, 2019 reply Follow Share @Shaik Masthan For that gate 2014 questions ..the schedule is serializable because no cycle in graph ..its so happened coincidently that if we consider commit or not ..in both cases no cycle for that question ...diagram given by @Mk Utkarsh is correct i think .. 0 votes 0 votes Please log in or register to add a comment.
0 votes 0 votes Serializable but not recoverable.. Sanandan answered Aug 23, 2020 Sanandan comment Share Follow See all 0 reply Please log in or register to add a comment.