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Recent questions tagged transaction-and-concurrency

17 votes

1 answer

361

How many recoverable schedules are possible from T1 and T2?
Consider the following Two Transactions. A) How many recoverable schedules can be formed over $T_{1}$ & $T_{2}$ ? $51$ $52$ $55$ $56$ B) How many cascadeless recoverable schedules can be formed over $T_{1}$ & $T_{2}$ ? $41$ $42$ $45$ $50$

nilamd asked in Databases Dec 21, 2015

by nilamd

3.7k views

5 votes

2 answers

362

view serializability
t1 t2 w(x) r(x) w(x) commit commit Why is this not view serializable?

divya_theodore asked in Databases Nov 14, 2015

by divya_theodore

1.3k views

5 votes

1 answer

363

How many conflict serializable schedules are possible ?
The transactions $T1$ and $T2$ are given as follows: $T1$: $R1(A)$ $W1(A)$ $R1(B)$ $W1(B)$ $T2$ : $R2(B)$ $W2(B)$ $R2(C)$ $W2(C)$ The total number of conflicts serializable that can be formed by $T1$ and $T2$ are Answer :20 (incorrect) The correct answer is 14

radha gogia asked in Databases Oct 20, 2015

2.5k views

1 vote

1 answer

364

Unrepeatable read problem

Shefali asked in Databases Oct 11, 2015

3.3k views

4 votes

2 answers

365

How is this schedule not allowed in Strict 2PL, but allowed in 2PL ?
$\begin{bmatrix} T1 &T2 \\ R(A) & \\ W(A)& \\ & R(A)\\ & W(A)\\ &R(B) \\ &W(B) \\ & Commit\\ Abort& \end{bmatrix}$ How is this schedule allowed in 2PL ? In 2PL ... phase in , which is not present in T2 ..? This example is given in the book by Raghu Ramkrishnan on page 529 and 552 (for reference)

learncp asked in Databases Oct 8, 2015

2.1k views

2 votes

2 answers

366

In 2 Phase locking protocol, how does a deadlock happen ?
According to 2-phase locking protocol, if a transaction acquires an exclusive lock on any object, another transaction cannot obtain any kind of lock on it till the first transaction unlocks it. Is the reverse also true, i.,e., if ... cannot acquire any kind of lock on it..? or it cannot acquire exclusive lock, but can acquire shared lock. ?

learncp asked in Databases Sep 29, 2015

2.1k views

1 vote

3 answers

367

How to check the view serializability of a given schedule ?
Suppose we have a schedule containing two transactions as shown- ... , for A we will get t1->t2, and for B we will get t1->t2.. Same graph will be obtained if we draw a single polygraph

learncp asked in Databases Sep 19, 2015

1.3k views

8 votes

1 answer

368

What is the difference between a Strict schedule and a Cascadeless schedule ?
I am unable to differentiate between a strict schedule and a cascadeless schedule...although what I have understood is that in strict schedule, we cannot perform read/write till the other transaction commits..but isnt this condition also valid for cascadeless schedules ? Can someone please explain by giving an example.

learncp asked in Databases Sep 18, 2015

9.6k views

54 votes

5 answers

369

GATE CSE 2015 Set 3 | Question: 29
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

go_editor asked in Databases Feb 15, 2015

11.1k views

53 votes

5 answers

370

GATE CSE 2015 Set 2 | Question: 46
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); ( ... Undo: T3, T1; Redo: T2 Undo: T3, T1; Redo: T2, T4 Undo: none; Redo: T2, T4, T3, T1 Undo: T3, T1, T4; Redo: T2

go_editor asked in Databases Feb 13, 2015

20.1k views

30 votes

4 answers

371

GATE CSE 2015 Set 2 | Question: 1
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

go_editor asked in Databases Feb 12, 2015

8.7k views

6 votes

3 answers

372

Consider 3 transactions T1, T2 and T3 having 2, 3 and 4 operations respectively.
Consider $3$ transactions $T_1, T_2$ and $T_3$ having $2, 3$ and $4$ operations respectively. Find the number of concurrent schedules?

Vikrant Singh asked in Databases Jan 29, 2015

by Vikrant Singh

16.1k views

1 vote

1 answer

373

please explain with the help of example WW problem and lost update problem and what is the difference between them?

neha pawar asked in Databases Nov 4, 2014

1.6k views

37 votes

1 answer

374

GATE IT 2005 | Question: 67
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

Ishrat Jahan asked in Databases Nov 4, 2014

by Ishrat Jahan

5.7k views

29 votes

1 answer

375

GATE IT 2005 | Question: 24
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

Ishrat Jahan asked in Databases Nov 3, 2014

by Ishrat Jahan

5.2k views

40 votes

6 answers

376

GATE IT 2004 | Question: 77
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 $T2,T1$

Ishrat Jahan asked in Databases Nov 2, 2014

by Ishrat Jahan

9.3k views

32 votes

5 answers

377

GATE IT 2004 | Question: 21
Which level of locking provides the highest degree of concurrency in a relational database ? Page Table Row Page, table and row level locking allow the same degree of concurrency

Ishrat Jahan asked in Databases Nov 2, 2014

by Ishrat Jahan

13.0k views

48 votes

5 answers

378

GATE IT 2007 | Question: 66
Consider the following two transactions$: T1$ and $T2.$ ...

Ishrat Jahan asked in Databases Oct 30, 2014

by Ishrat Jahan

13.9k views

37 votes

7 answers

379

GATE IT 2008 | Question: 63
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

Ishrat Jahan asked in Databases Oct 29, 2014

by Ishrat Jahan

14.4k views

0 votes

1 answer

380

time stamp ordering
Consider the following sequence of actions. r1(A) r2(B) w1(C) r3(B) r3(C) w2(B) w3(A) Which of the following time stamp ordering allowed to execute the schedule using basic time stamp protocol? A) (T1, T2, T3) = (10, 30, 20) B) (T1, T2, T3) = (20, 30, 10) C) (T1, T2, T3) = (30, 20, 10) D) (T1, T2, T3) = (10, 20, 30)

Keith Kr asked in Databases Oct 19, 2014

1.1k views

27 votes

4 answers

381

GATE CSE 2010 | Question: 42
Consider the following schedule for transactions $T1, T2$ and $T3:$ ... correct serialization of the above? $T1 \to T3 \to T2$ $T2 \to T1 \to T3$ $T2 \to T3 \to T1$ $T3 \to T1 \to T2$

go_editor asked in Databases Sep 30, 2014

8.6k views

47 votes

6 answers

382

GATE CSE 2010 | Question: 20
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

go_editor asked in Databases Sep 29, 2014

19.9k views

26 votes

2 answers

383

GATE CSE 2014 Set 3 | Question: 29
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.

go_editor asked in Databases Sep 28, 2014

6.7k views

51 votes

3 answers

384

GATE CSE 2014 Set 2 | Question: 29
Consider the following schedule S of transactions $T1, T2, T3, T4:$ ... S is not conflict-serializable but is recoverable S is both conflict-serializable and recoverable S is neither conflict-serializable not is it recoverable

go_editor asked in Databases Sep 28, 2014

23.7k views

23 votes

2 answers

385

GATE CSE 2014 Set 1 | Question: 29
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? $r_1(x)$; $r_2(x)$; $w_1(x)$; $r_3(x)$; $w_2(x)$; $r_2(x)$; ... $r_1(x)$; $w_2(x)$; $w_1(x)$; $r_2(x)$; $w_2(x)$; $r_3(x)$; $r_1(x)$; $w_1(x)$;

go_editor asked in Databases Sep 26, 2014

7.0k views

61 votes

7 answers

386

GATE CSE 2012 | Question: 27
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

Arjun asked in Databases Sep 25, 2014

by Arjun

17.7k views

47 votes

3 answers

387

GATE CSE 1999 | Question: 2.6
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

Kathleen asked in Databases Sep 23, 2014

11.2k views

28 votes

2 answers

388

GATE CSE 2009 | Question: 43
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

Kathleen asked in Databases Sep 22, 2014

5.2k views

25 votes

5 answers

389

GATE CSE 2007 | Question: 64
Consider the following schedules involving two transactions. Which one of the following statements is TRUE? $S_1 :r_1(X); r_1(Y); r_2(X); r_2(Y); w_2(Y); w_1(X)$ ... is not conflict serializable. $S_1$ is not conflict serializable and $S_2$ is conflict serializable. Both $S_1$ and $S_2$ are not conflict serializable.

Kathleen asked in Databases Sep 22, 2014

7.6k views

65 votes

9 answers

390

GATE CSE 2006 | Question: 20, ISRO2015-17
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 $=12000$ new $=10000$ ... $3$ because transaction T1 has committed We can apply redo and undo operations in arbitrary order because they are idempotent

Rucha Shelke asked in Databases Sep 17, 2014

by Rucha Shelke

23.5k views

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Recent questions tagged transaction-and-concurrency