# Recent questions tagged serializability 1 vote
1
Consider the following four schedules due to three transactions (indicated by the subscript) using read and write on a data item $x$, denoted by $r(x)$ and $w(x)$respectively. Which one of them is conflict serializable? $r_1(x);r_2(x);w_1(x);r_3(x);w_2(x)$ $r_2(x);r_1(x);w_2(x);r_3(x);w_1(x)$ $r_3(x);r_2(x);r_1(x);w_2(x);w_1(x)$ $r_2(x);w_2(x);r_3(x);r_1(x);w_1(x)$ $1$ $2$ $3$ $4$
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A' is set of all possible schedules 'C' is set of all possible schedules that are guaranteed to produce a correct final result 'S' is the set of all serializable schedules 'P' is the set of all schedules possible under 2-phase locking protocol Which is FALSE? $P\subseteq C$ $S\subset P$ $S\subseteq P$ $P\subset C$
1 vote
3
Consider the following schedules with data item x The number of serial schedules which are view equal to schedules but not conflict equal is ___________.
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I am getting the answer as c but the given answer is b. How b can be ans, there is a cycle R1x->W1x (s1->s2) and W1y->w1y(s2->s1),so s1,s2 can not be conflict serializable… i m confused.. what is the right answer?
1 vote
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A schedule S contains three transactions $T_1$, $T_2$, $T_3$ and the oeprations sequence is given below: $T_1$: $Read$ $A$; $T_2$: $Write$ $A$; $T_3$: $Read$ $A$; $T_1$: $Write$ $A$; $T_3$: $Write$ $A$ and all the above transactions ... Is the above schedule is serializable or not? If yes it is equivalent to which serial schedule. Find the proper combination of the given alternatives from I to VII
1 vote
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1 vote
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T1 T2 T3 R(X) W(X) commit W(X) commit R(X) commit is this transaction conflict serializable and view serializable?
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T1 T2 T3 W(Y) commit R(X) R(Y) W(Z) commit W(X) commit is this schedule a strict schedule?
1 vote
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Tl:W(X), T2:R(X), Tl:W(X), T2:Commit, Tl:Abort is this schedule conflict serializable?
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Tl:R(X), T1:R(Y), T1:W(X), T2:R(Y), T3:W(Y), Tl:W(X), T2:R(Y) is this schedule view serializable?
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https://gateoverflow.in/1484/gate1999-2-6 in this questions after T2 is not granted exclusive lock on A does the transaction T2 gets blocked entirely or it can continue to acquire exclusive lock on B? and if T2 continues to acquire lock on B followed by T1 requesting for read and write lock on B successively, is it deadlock situation here? And is that why it is not 2PL?
1 vote
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I am looking for some clarity on this topic. Here is some random schedule as an example: $r1(x) w1(x) r2(x) w2(x) r3(y) r3(x) w3(x) c3 a1 c2$ I was told, that for conflict serializablity we simply ignore the aborted transaction, ... not ignored for recoverability, strictness or avoidance of cascading rollbacks. I would be grateful if the question would be answered since this really confuses me.
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S1: R(A) W(A) W(B) S2: R(A) W(A) R(B) W(B) How many view serializable schedules are possible which are not conflict serializable? (A) 0 (B) 1 (C) 2 (D) 3
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Which of the following statement is true? 1. time stamp protocol may not result recoverable schedule 2. in 2PL, No data are affected until all locks are obtained i.e., until the transaction is in its locked point. a) only a b) only b c) a and b d) none
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T1 T2 W(x) R(x) W(x) ABORT COMMIT
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The above question has a blind write so it should be View Serializable. But can it be Conflict Serializable?
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Consider the following schedule: S:R2(A) W1(B) W1(C) R3(B) R2(B) R1(A) C1 R2(C) C2 W3(A)C3 Please explain how it is allowed in 2 PL
1 vote
20
If total n! serial schedules are possible , will all of them give the same result?
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State True or False and Tell reason 1) 2PL is always conflict serializable 2)Timestamp protocol is conflict and view serializable
1 vote
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Why is cascading rollback possible in 2 phase locking protocol, we know it guarantee serializability and serializable schedule are strict, which implies it is cascadeless? Please clear the doubt and correct me.
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Consider the following transactions T1:r1(A) w1(A) r1(B) w1(B) T2:r2(B) w2(B) r2(A) w2(A) 1) How many schedules serializable as T1->T2 2) How many schedules serializable as T2->T1
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Draw the polygraph and explain whether it is view-serializable or not?