Recent questions tagged transactions - GATE CSE Doubts

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Serialisability in Blind write
I read one Gate question and in Korth's book that if a schedule contains blind write then it is not conflict serialisable. I am not able to understand the reason. This is the gate question – https://gateoverflow.in/302837/gate2019-11 I also read that timestamp protocol allows conflict serializable schedules.

asked Oct 12 in Databases by vizzard110 (85 points) | 10 views

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Self Doubt on Transcation & Concurrency Control
Why this schedule is not View Serializable?? Anyone please elaborate this.

asked Sep 7 in Databases by AbhayPrajapati (7 points) | 34 views

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Raghu Ramkrishnan - Transactions and Concurrency Control

asked Aug 30 in Databases by pritishc (23 points) | 55 views

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Self doubt DBMS Conflict Equivalent schedules
$\text{Consider the transactions given below}$ What are the number of conflict equivalent schedules possible What is the approach to solve such questions T1 T2 T3 $r_{A}$ $w_{B}$ $r_{A}$ $w_{B}$ $r_{A}$ $w_{B}$

asked Aug 26 in Databases by Shashank Rustagi (513 points) | 38 views

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Serializability
Are all serializable schedules recoverable, cascade-less, strict???

asked Aug 4 in Databases by manas_kulkarni (1 point) | 29 views

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Conflict Equivalence-Databases (Self doubt)
consider statement 1 : Two schedules are conflict equivalent when the precedence graphs are isomorphic. Is this statement correct or wrong. It is the counter example for the same S1: = R1(A) R2(A)W1(A) W2(A) S2: = R1(A) ... present in both schedules ( say T1 and T2) must be same.Is this also the condition for checking Conflict Equivalency check?

asked Jul 9 in Databases by prajjwalsingh_11 (13 points) | 6 views

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deadlock in databases
my question is isn’t wait wound and wait die deadlock prevention algo so how can we say that they are deadlock avoidance and how they can cause more aborts than needed?

asked Jun 25 in Databases by abcd9982 (87 points) | 10 views

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GATE2017-2-44 Video Solution
Two transactions $T_1$ and $T_2$ are given as $T_1:r_1(X)w_1(X)r_1(Y)w_1(Y)$ $T_2:r_2(Y)w_2(Y)r_2(Z)w_2(Z)$ where $r_i(V)$ denotes a $\textit{read}$ operation by transaction $T_i$ on a variable $V$ and $w_i(V)$ denotes a ... by transaction $T_i$ on a variable $V$. The total number of conflict serializable schedules that can be formed by $T_1$ and $T_2$ is ______

asked Apr 18 in Databases by admin (193 points) | 10 views

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GATE2006-20, ISRO2015-17 Video Solution
Consider the following log sequence of two transactions on a bank account, with initial balance $12000,$ that transfer $2000$ to a mortgage payment and then apply a $5\%$ interest. T1 start T1 B old $=1200$ new $=10000$ T1 ... $2$ and $3$ because transaction T1 has committed We can apply redo and undo operations in arbitrary order because they are idempotent

asked Apr 18 in Databases by admin (193 points) | 5 views

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GATE2010-20 Video Solution
Which of the following concurrency control protocols ensure both conflict serializability and freedom from deadlock? 2-phase locking Time-stamp ordering I only II only Both I and II Neither I nor II

asked Apr 18 in Databases by admin (193 points) | 3 views

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GATE2015-2-46 Video Solution
Consider a simple checkpointing protocol and the following set of operations in the log. (start, T4); (write, T4, y, 2, 3); (start, T1); (commit, T4); (write, T1, z, 5, 7); (checkpoint); (start, T2); (write, T2, x, 1, 9); (commit, T2); (start, T3); (write, ... Undo: T3, T1; Redo: T2 Undo: T3, T1; Redo: T2, T4 Undo: none; Redo: T2, T4, T3, T1 Undo: T3, T1, T4; Redo: T2

asked Apr 18 in Databases by admin (193 points) | 7 views

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GATE2016-1-51 Video Solution
Consider the following two phase locking protocol. Suppose a transaction $T$ accesses (for read or write operations), a certain set of objects $\{O_1,\ldots,O_k \}$. This is done in the following ... -freedom guarantee neither serializability nor deadlock-freedom guarantee serializability but not deadlock-freedom guarantee deadlock-freedom but not serializability.

asked Apr 18 in Databases by admin (193 points) | 4 views

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GATE2016-2-51 Video Solution
Consider the following database schedule with two transactions $T_{1}$ and $T_{2}$ ... schedule is TRUE? $S$ is non-recoverable. $S$ is recoverable, but has a cascading abort. $S$ does not have a cascading abort. $S$ is strict.

asked Apr 18 in Databases by admin (193 points) | 4 views

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GATE2012-27 Video Solution
Consider the following transactions with data items $P$ and $Q$ initialized to zero: ${\begin{array}{|c|l|r|c|}\hline \textbf{$ ... leads to a serializable schedule a schedule that is not conflict serializable a conflict serializable schedule a schedule for which a precedence graph cannot be drawn

asked Apr 18 in Databases by admin (193 points) | 6 views

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GATE2014-2-29 Video Solution
Consider the following schedule S of transactions $T1, T2, T3, T4:$ ... recoverable S is not conflict-serializable but is recoverable S is both conflict-serializable and recoverable S is neither conflict-serializable not is it recoverable

asked Apr 18 in Databases by admin (193 points) | 7 views

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GATE2016-2-22 Video Solution
Suppose a database schedule $S$ involves transactions $T_1,........,T_n$ . Construct the precedence graph of $S$ with vertices representing the transactions and edges representing the conflicts.If $S$ is serializable, which one ... guaranteed to yield a serial schedule? Topological order Depth-first order Breadth- first order Ascending order of the transaction indices

asked Apr 18 in Databases by admin (193 points) | 5 views

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GATE1999-2.6 Video Solution
For the schedule given below, which of the following is correct: ... schedule is not serializable but can occur in a scheme using 2PL protocol This schedule is not serializable and cannot occur in a scheme using 2PL protocol

asked Apr 18 in Databases by admin (193 points) | 5 views

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GATE2007-IT-66 Video Solution
Consider the following two transactions : T1 and T2. T1 : read (A); T2 : read (B); read (B); read (A); if A = 0 then B ← B + 1; if B ≠ 0 then A ← A - 1; write (B); write (A); Which of the following schemes, using shared and exclusive locks, satisfy the ... ← B + 1; then A ← A - 1; write (B); write (A); unlock (A); unlock (A); unlock (B); unlock (B); commit; commit;

asked Apr 18 in Databases by admin (193 points) | 4 views

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GATE2003-29, ISRO2009-73 Video Solution
Which of the following scenarios may lead to an irrecoverable error in a database system? A transaction writes a data item after it is read by an uncommitted transaction A transaction reads a data item after it is read by an ... it is written by a committed transaction A transaction reads a data item after it is written by an uncommitted transaction

asked Apr 18 in Databases by admin (193 points) | 6 views

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GATE2015-3-29 Video Solution
Consider the partial Schedule $S$ involving two transactions $T1$ and $T2$. Only the $\textit{read}$ and the $\textit{write}$ operations have been shown. The $\textit{read}$ operation on data item $P$ ... re-started to ensure transaction atomicity Schedule $S$ is recoverable and can ensure transaction atomicity and nothing else needs to be done

asked Apr 18 in Databases by admin (193 points) | 3 views

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GATE2019-11 Video Solution
Consider the following two statements about database transaction schedules: Strict two-phase locking protocol generates conflict serializable schedules that are also recoverable. Timestamp-ordering concurrency control protocol with Thomas' Write Rule can generate view serializable ... the above statements is/are TRUE? I only II only Both I and II Neither I nor II

asked Apr 18 in Databases by admin (193 points) | 7 views

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GATE2008-IT-63 Video Solution
Consider the following three schedules of transactions T1, T2 and T3. [Notation: In the following NYO represents the action Y (R for read, W for write) performed by transaction N on object O.] ... equivalent to each other S2 is conflict equivalent to S3, but not to S1 S1 is conflict equivalent to S2, but not to S3

asked Apr 18 in Databases by admin (193 points) | 2 views

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GATE2004-IT-77 Video Solution
Consider the following schedule $S$ of transactions $T1$ and $T2:$ ... only as $T2, T1$ $S$ is serializable both as $T1, T2$ and $T2, T1$ $S$ is not serializable either as $T1,T2$ or as $T2,T1$

asked Apr 18 in Databases by admin (193 points) | 4 views

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GATE2015-2-1 Video Solution
Consider the following transaction involving two bank accounts $x$ and $y$. read(x); x:=x-50; write (x); read(y); y:=y+50; write(y) The constraint that the sum of the accounts $x$ and $y$ should remain constant is that of Atomicity Consistency Isolation Durability

asked Apr 18 in Databases by admin (193 points) | 8 views

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GATE2010-42 Video Solution
Consider the following schedule for transactions $T1, T2$ and $T3:$ ... correct serialization of the above? $T1 \to T3 \to T2$ $T2 \to T1 \to T3$ $T2 \to T3 \to T1$ $T3 \to T1 \to T2$

asked Apr 18 in Databases by admin (193 points) | 3 views

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GATE2014-1-29 Video Solution
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? $r_1(x)$; $r_2(x)$; $w_1(x)$; $r_3(x)$; $w_2(x)$; $r_2(x)$ ... $r_1(x)$; $w_2(x)$; $w_1(x)$; $r_2(x)$; $w_2(x)$; $r_3(x)$; $r_1(x)$; $w_1(x)$;

asked Apr 18 in Databases by admin (193 points) | 4 views

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GATE2003-87 Video Solution
Consider three data items $D1, D2,$ and $D3,$ and the following execution schedule of transactions $T1, T2,$ and $T3.$ In the diagram, $R(D)$ and $W(D)$ denote the actions reading and writing the data item $D$ ... $T2; T1; T3$ The schedule is serializable as $T3; T2; T1$ The schedule is not serializable

asked Apr 18 in Databases by admin (193 points) | 1 view

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GATE2014-3-29 Video Solution
Consider the transactions $T1, T2, \:\text{and} \:T3$ and the schedules $S1 \:\text{and} \:S2$ given below. $T1: r1(X); r1(Z); w1(X); w1(Z) $ $T2: r2(Y); r2(Z); w2(Z) $ $T3: r3(Y); r3(X); w3(Y) $ ... ? Only $S1$ is conflict-serializable. Only $S2$ is conflict-serializable. Both $S1$ and $S2$ are conflict-serializable. Neither $S1$ nor $S2$ is conflict-serializable.

asked Apr 18 in Databases by admin (193 points) | 2 views

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GATE2007-64 Video Solution
Consider the following schedules involving two transactions. Which one of the following statements is TRUE? $S_1 :r_1(X); r_1(Y); r_2(X); r_2(Y); w_2(Y); w_1(X)$ $S_2 :r_1(X); r_2(X); r_2(Y); w_2(Y); r_1(Y); w_1(X)$ ... $S_1$ is not conflict serializable and $S_2$ is conflict serializable. Both $S_1$ and $S_2$ are not conflict serializable.

asked Apr 18 in Databases by admin (193 points) | 2 views

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GATE2016-1-22 Video Solution
Which one of the following is NOT a part of the ACID properties of database transactions? Atomicity Consistency Isolation Deadlock-freedom

asked Apr 18 in Databases by admin (193 points) | 3 views

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GATE2009-43 Video Solution
Consider two transactions $T_1$ and $T_2$, and four schedules $S_1, S_2, S_3, S_4$, of $T_1$ and $T_2$ as given below: $T_1: R_1[x]W_1[x]W_1[y]$ $T_2: R_2[x]R_2[y]W_2[y]$ $S_1: R_1[x]R_2[x]R_2[y] W_1[x] W_1[y] W_2[y]$ ... $S_1 \text{ and } S_2$ $S_2 \text{ and } S_3$ $S_3$ only $S_4$ only

asked Apr 18 in Databases by admin (193 points) | 6 views

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GATE2005-IT-67 Video Solution
A company maintains records of sales made by its salespersons and pays them commission based on each individual's total sales made in a year. This data is maintained in a table with following schema: salesinfo = (salespersonid, ... running concurrently throughout Execute T3 followed by T2; T1 running concurrently throughout Execute T3 followed by T2 followed by T1

asked Apr 18 in Databases by admin (193 points) | 5 views

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GATE2005-IT-24 Video Solution
Amongst the ACID properties of a transaction, the 'Durability' property requires that the changes made to the database by a successful transaction persist Except in case of an Operating System crash Except in case of a Disk crash Except in case of a power failure Always, even if there is a failure of any kind

asked Apr 18 in Databases by admin (193 points) | 4 views

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Made easy database management system page 31 ques 32

asked Apr 15 in Databases by Setika Mehra (5 points) | 11 views

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Made easy database management system page 28 ques 13

asked Apr 15 in Databases by Setika Mehra (5 points) | 14 views

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TRANSACTIONS AND CONCURRENCY CONTROL GATE 2017-2marks

asked Jan 30 in Databases by kshubham538 (-31 points) | 36 views

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Applied course test series : Transactions serializability

asked Jan 3 in Databases by vishal burnwal (65 points) | 126 views

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Ace Mock Test 1 2020 Q48
please explain how to check 2PL?

asked Dec 27, 2019 in Databases by ssap09 (13 points) | 42 views

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self doubt DBMS
I need some reference for Conservative 2PL. I referred many links. But no mentions how locks are released. So by default if we take that protocol doent have any restriction on time when locks gets realesed then it might have irrecoverable schedules. But on ... I could not find any reference for this protocol in standard book. So if someone have any reference please provide. thanks.

asked Dec 24, 2019 in Databases by Vimal Patel (1.5k points) | 15 views

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Applied course test series : Transactions
For above question my doubt is that whether the given schedule is view serializable or not, because i am getting it as not view serializable. And since the schedule is not serializable so it cannot be allowed under thomas write rule. So ... .And it is allowed under thomas write rule.So they provided 1 as answer. Can someone explain which is correct?

asked Dec 20, 2019 in Databases by vishal burnwal (65 points) | 62 views

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