Recent questions tagged transactions - GATE CSE Doubts

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Tga test series
Why dirty read ? Here T2 was commited after the T1....what about the option c?

asked Feb 5 in Databases by Enolx.21 (49 points) | 11 views

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Self Doubt , Databases
Is Read – Write conflict possible in a strict recoverable schedule? As strict 2PL guarantees strict recoverable. Is Read-Write conflict possible in a strict recoverable schedule ?

asked Jan 24 in Databases by anurags228 (23 points) | 8 views

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Cascade Rollback and Not recoverable at the same time

asked Jan 18 in Databases by reboot (5 points) | 9 views

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Databases: recoverability
Assume $S$ is a schedule that has both read and write oeration with different transaction with different data variable. Also assume all the operations are atomic in nature. Which of the following is true? $S$ with no dirty read then $S$ is cascadeless ... own set of data variables. If so then there is no lost update, no cascading rollback and so it is strict recoverable.

asked Dec 24, 2020 in Databases by ytheuyr (2 points) | 5 views

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no of rollback for failed transactions
(Say) transactions data dependency(dirty read) are in the order T1→ T2 → T3 → …..Tn ( Here A→ B means A write and B read). So after Tn read if T1 failed then what should be the no. of transactions need to rollback Are we also need to include failed(T1) transaction in no. of transaction need to be rolled back? what should be the answer n or (n-1)?

asked Dec 19, 2020 in Databases by wander (301 points) | 12 views

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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, 2020 in Databases by vizzard110 (85 points) | 12 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, 2020 in Databases by AbhayPrajapati (7 points) | 41 views

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Raghu Ramkrishnan - Transactions and Concurrency Control

asked Aug 30, 2020 in Databases by pritishc (27 points) | 74 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, 2020 in Databases by ijnuhb (741 points) | 44 views

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

asked Aug 4, 2020 in Databases by manas_kulkarni (1 point) | 31 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, 2020 in Databases by prajjwalsingh_11 (15 points) | 7 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, 2020 in Databases by abcd9982 (87 points) | 21 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, 2020 in Databases by admin (573 points) | 24 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, 2020 in Databases by admin (573 points) | 12 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, 2020 in Databases by admin (573 points) | 4 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, 2020 in Databases by admin (573 points) | 14 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, 2020 in Databases by admin (573 points) | 9 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, 2020 in Databases by admin (573 points) | 17 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, 2020 in Databases by admin (573 points) | 15 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, 2020 in Databases by admin (573 points) | 12 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, 2020 in Databases by admin (573 points) | 6 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, 2020 in Databases by admin (573 points) | 9 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, 2020 in Databases by admin (573 points) | 10 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, 2020 in Databases by admin (573 points) | 10 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, 2020 in Databases by admin (573 points) | 9 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, 2020 in Databases by admin (573 points) | 9 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, 2020 in Databases by admin (573 points) | 6 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, 2020 in Databases by admin (573 points) | 7 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, 2020 in Databases by admin (573 points) | 14 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, 2020 in Databases by admin (573 points) | 6 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, 2020 in Databases by admin (573 points) | 6 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, 2020 in Databases by admin (573 points) | 8 views

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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, 2020 in Databases by admin (573 points) | 4 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, 2020 in Databases by admin (573 points) | 5 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, 2020 in Databases by admin (573 points) | 5 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, 2020 in Databases by admin (573 points) | 16 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, 2020 in Databases by admin (573 points) | 14 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, 2020 in Databases by admin (573 points) | 16 views

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Made easy database management system page 31 ques 32

asked Apr 15, 2020 in Databases by Setika Mehra (13 points) | 13 views

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Made easy database management system page 28 ques 13

asked Apr 15, 2020 in Databases by Setika Mehra (13 points) | 17 views

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