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Recent questions tagged concurrency

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Concurrent program
Consider the concurrent program: x:=1; cobegin x:= x + x + 1|| x:= x + 2 coend; Reading and writing of a vairable is atomic, but evaluation of an expression is not atomic. The sum of possible values of variable x at the end of execution of the program is ___. The above question ... + 2 = 3 now again running x = 1+ x + 1 and now substituting the value of x as 3 x = 1 + 3 + 1 = 5

Chaitanya Kale asked in Operating System Nov 22, 2022

by Chaitanya Kale

142 views

2 votes

1 answer

2

Gate Wallah Study material
Please help with the minimum value. Problem is from the gate wallah study handout.

joleyasarthak asked in Operating System Nov 21, 2022

by joleyasarthak

478 views

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Best Open Video Playlist for Concurrency and Synchronization Topic | Operating Systems
Please list out the best free available video playlist for Concurrency and Synchronization from Operating Systems as an answer here (only one playlist per answer). We'll then select the best playlist and add to GO ... are more likely to be selected as best. For the full list of selected videos please see here

makhdoom ghaya asked in Study Resources Aug 20, 2022

by makhdoom ghaya

69 views

1 vote

2 answers

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Is a Serial Schedule always Recoverable?
Is only conflict serializable schedules are recoverable? Or both view as well as conflict serializable schedules are recoverable? I have been seeing different answers in different forum.

DebRC asked in Databases Aug 16, 2022

by DebRC

792 views

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concurrency control
question about concurrency control methods

jayadev asked in Databases Jul 3, 2022

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4 votes

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made east test series - synchronization - OS
Consider the following proposed solution to Dining Philosopher's problem to avoid deadlock. The binary semaphore lock is initialized to 1. Which of the following is correct? Removing (i) and (ii) will not affect the code. It will work fine. Removing (iii) ... fine. All (i), (ii), (iii) and (iv) are necessary. Removal of any of them will affect the code.

atulcse asked in Operating System Jan 19, 2022

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1 answer

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Transactions and concurrency control
When Ti attempts to write data item Q, if TS(Ti ) < w-timestamp(Q), then Ti is attempting to write an obsolete value of {Q}. Rather than rolling back Ti as the timestamp ordering protocol would have done, this {write} operation can be ... Ti any transaction which comes after the Ti will have a chance of reading that change made by Ti by performing Read(Q) .

jayadev asked in Databases Dec 30, 2021

336 views

1 vote

2 answers

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Virtual Gate Test Series: Operating System - Fork-Join Concurrency Structure
Consider the code fragment: count = 3; S1; Fork L1; L1: S3; S2; goto L3; S4; Fork L2; L2: S6; goto L3; S5; L3: join count S7 Which one of the following represents correct precedence graph of the above code fragment? the answer is given but I’m getting where am I wrong?

aditi19 asked in Operating System Jun 12, 2019

3.4k views

1 vote

2 answers

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Gate 2019- minimum D value in OS concurrent process question
Why the value of D is 80 in concurrent process question and not 0? The question didn't mention that each statement take 3 instruction to execute so why assume that?

Ankit Sahu asked in Operating System Feb 4, 2019

1.0k views

2 votes

1 answer

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Self doubt, 2PL
Is different 2 phase locking a subset of each other? For example, if the schedule is Strict 2PL then it will also be simple 2PL. Something like a 2PL is a subset of Strict 2PL is a subset of rigorous 2PL.

vinay chauhan asked in Databases Jan 18, 2019

by vinay chauhan

396 views

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2 answers

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How Strict 2PL avoids unrepeatable read problem?
Please explain. Use the below transaction.

susgir2 asked in Databases Jan 4, 2019

1.3k views

2 votes

3 answers

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MadeEasy Test Series: Operating System - Process Synchronization
P1 terminates but P2 does not P2 terminates but P1 does not Both P1 and P2 terminate Neither P1 nor P2 terminate

Sambhrant Maurya asked in Operating System Jan 3, 2019

by Sambhrant Maurya

1.3k views

2 votes

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Self Doubt: Is this schedule conflict Serializable?
My question, does abort in T2 makes this schedule conflict serializable? as the effect of T2 will be null. T1: Rx T2: Wx T1: Wx T2: ABORT T1: COMMIT Rx – read item x. Wx – write item x.

susgir2 asked in Databases Dec 31, 2018

381 views

1 vote

0 answers

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TRANSACTIONS
ANY EXAMPLE OF AN SCHEDULE WHICH IS RECOVERABLE BUT NOT CASCADLESS.?

junaid ahmad asked in Databases Dec 21, 2018

by junaid ahmad

185 views

1 vote

1 answer

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[Personal Doubt] View Serializability
Is every serializable schedule view serializable?, or like conflict serializable, there could be a serializable schedule which isn’t view serializable?

shreejeetp asked in Databases Dec 14, 2018

234 views

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GA Test series
pls explain why C is correct not A? isn’t every schedule that is supported by 2PL conflict serializable?

aditi19 asked in Databases Dec 8, 2018

250 views

1 vote

1 answer

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2 Phase Locking
is it supported by 2PL?

aditi19 asked in Databases Dec 8, 2018

426 views

0 votes

1 answer

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Raghuramkrishnan
T1: R(X), T2: W(X), T2: commit, T1: W(X), T1: commit, T3: R(X), T3: commit is this allowed in Thomas write rule? if yes then what will be the serial order

aditi19 asked in Databases Dec 1, 2018

936 views

1 vote

1 answer

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2PL Doubt
T1: W(X), T2: R(Y), T1: R(Y), T2: R(X) does 2PL protocol allows it? T1 T2 L-X(X) W(X) L-S(Y) R(Y) U(X) L-S(Y) R(Y) L-S(X) R(X) here T2 is granted lock on X as T1 enters shrinking phase as no exclusive locks are held on X is my solution correct?

aditi19 asked in Databases Nov 25, 2018

355 views

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#easy book
T1 T2 R(X) W(X) W(X) aborts commit find conflict serializability,view serializability, recoverable,cascadeless and strict schedule

amit166 asked in Databases Oct 26, 2018

270 views

1 vote

0 answers

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Syllabus of Database management system
Are following part of gate syllabus for dbms? 1-Validation Based protocols 2-multiversion schemes 3-snapshot isolation 4-predicate reads(concurrency control) 5-concurrency in index structures.

bts1jimin asked in Databases Aug 27, 2018

911 views

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1 answer

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Timestamp Ordering Protocol
Suppose that transaction Ti issues write(Q). According to timestamp Ordering protocol: If TS(Ti)<R-timestamp(Q) then Ti will rollback. My doubt is if TS(Ti) < R-timestamp(Q),it means write operation is occurring before the read operation and ... the transaction is reading the correct value of Q.Then why is it rolling back? Please correct me where am I going wrong.

Bhagyashree Mukherje asked in Databases Jul 28, 2018

by Bhagyashree Mukherje

1.3k views

1 vote

0 answers

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Understanding multiversion timestamp ordering protocol in database systems
I was reading multiversion timestamp ordering protocol from the book Database Systems Concepts by Korth. It can be explained in simpler words as follows: Each data item version $Q$ has two timestamps associated with it: W-timestamp: ... I am wrong and it was indeed asked in previous year GATE paper?) Can we safely skip it?

GateAspirant999 asked in Databases May 21, 2018

by GateAspirant999

2.9k views

1 vote

1 answer

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Dirty Read
Correct me where i am wrong if i am wrong Please :) Dirty Read means Reading the data of uncommited transaction. For removing the Dirty read we should always read after the transaction which wrote X commits , this is the only way to remove dirty read rt ? T1 T2 ... (x) Above Shown is The Only way of removing the Dirty read rt ? My doubt is its very similar to the Solution of Cascadeless.

Na462 asked in Databases Apr 12, 2018

by Na462

956 views

1 vote

1 answer

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Cascadeless/ Recoverable
The given schedule: R1 (A) R2 (B) W2 (B) W1(A) W2 (A) Commit2 R1 (C) is revoreable, cascadeless or strict?

budhu asked in Databases Jan 29, 2018

by budhu

1.2k views

1 vote

1 answer

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Strict and Conservative 2PL
We know, Conservative 2PL is another name of Strict 2PL. But According to Navathe book Conservative 2PL is deadlock free,but Strict 2PL can have deadlock. Then how both could be same??

srestha asked in Databases Jan 27, 2018

3.6k views

2 votes

0 answers

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Concurrency Control
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

hacker16 asked in Databases Jan 18, 2018

1.0k views

1 vote

0 answers

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Ace Test series: Databases - Transactions And Concurrency
Is MGL in syllabus ??

ashish pal asked in Databases Jan 10, 2018

250 views

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Recent questions tagged concurrency