# Recent questions tagged transactions

1 vote
1
Assume transaction $A$ holds a shared lock $R.$ If transaction $B$ also requests for a shared lock on $R.$ It will result in deadlock situation immediately be granted immediately be rejected be granted as soon as it is released by $A$
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When transaction $Ti$ requests a data item currently held by $Tj,Ti$ is allowed to wait only if it has a time stamp smaller than that of $Tj$ (that is $Ti$ is order than Tj). Otherwise, $Ti$ is rolled back (dies). This is Wait-die Wait-wound Wound-wait Wait
3
When transaction $Ti$ requests a data item currently held by $Tj,Ti$ is allowed to wait only if it has a timestamp smaller than that of $Tj$ (that is $Ti$ is order than Tj). Otherwise, $Ti$ is rolled back (dies). This is Wait-die Wait-wound Wound-wait Wait
4
Assume transaction $A$ holds a shared lock $R.$ If transaction $B$ also requests for a shared lock on $R.$ It will result in deadlock situation immediately be granted immediately be rejected be granted as soon as it is released by $A$
1 vote
5
In conservative two phase locking protocol, a transaction Should release all the locks only at the beginning of transaction Should release exclusive locks only after the commit operation Should acquire all the exclusive locks at the beginning of transaction Should acquire all the locks at the beginning of transaction
1 vote
6
Consider following schedules involving two transactions: $S_{1}: \: r_{1}(X);r_{1}(Y);r_{2}(X);r_{2}(Y);w_{2}(Y);w_{1}(X)$ $S_{2}: \: r_{1}(X);r_{2}(X);r_{2}(Y);w_{2}(Y);r_{1}(Y);w_{1}(X)$ Which of the ... . $S_1$ is conflict serializable and $S_2$ 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
1 vote
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During its execution, a transaction passes through several states, until it finally commits or aborts. List all possible sequences of states through which a transaction may pass. Explain why each state transition may occur.
10
Database-system implementers have paid much more attention to the ACID properties than have file-system implementers. Why might this be the case ?
11
Consider a file system such as the one on your favorite operating system. a. What are the steps involved in creation and deletion of files, and in writing data to a file ? b. Explain how the issues of atomicity and durability are relevant to the creation and deletion of files, and to writing data to files.
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Suppose that there is a database system that never fails. Is a recovery manager required for this system ?
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List the $ACID$ properties. Explain the usefulness of each.
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How can 2PL protocol ( simple one ) ensure conflict serializability even though it cannot ensure freedom from deadlock ? I mean ,if a schedule is conflict serializable it has a conflict equivalent to a serial schedule and serial schedules won't have deadlocks .Right ?
15
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?
16
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 schedules that are not ... Which of the above statements is/are TRUE? I only II only Both I and II Neither I nor II
1 vote
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T1 LOCK-X (A) LOCK-S (B) R(A) R(B) W(A) UNLOCK (A) COMMIT UNLOCK (B) is this following CONSERVATIVE 2PL ? doubt : in conservative locking schme ..all locks are aqured before starting but locks can be released at ANY time ..so conservative need not be strict/rigorous OR is it only after commit ??
18
Consider the following schedule $\text{S : r2(A), w1(B), w1(C), R3(B), r2(B), r1(A), commit_1, r2(C), commit_2, w3(A), commit_3 }$ Consider the following statements : S1 : Schedule(S) is conflict serializable schedule. S2 : Schedule(S) is allowed by 2PL. S3 : Schedule(S) is strict recoverable schedule. S4 : Schedule(S) is allowed by strict 2PL. How many above statements true about schedule(S) ?
19
how many view equivalent schedules are possible for the Sch given below:
1 vote
20
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.
21
Is the following schedule conflict serializable T1 T2 T3 W(X) commit R(X) W(X) R(X) W(X) commit W(X) commit
22
Q50. how many statements is true unrepeatable read also know as read write conflict Strict 2PL may have read write conflict 1st one given as true now my doubt is we know that read write conflict that is https://www.revolvy.com/page/Read%E2%80%93write-conflict and we also ... watch?v=mLNfpqybSZM . how we can call unrepeatable read as read write conflict 2nd one given as false but i think it is true
1 vote
23
Which of the following time stamp ordering protocol(s) allow the following schedules? $T:W_1(A)\ W_2(A)\ W_3(A)\ R_2(A)\ R_4(A)$ Time stamps: $T_1=5,T_2=10,T_3=15,T_4=20$ Thomas write rule Multiversion time stamp protocol Basic Time stamp All of these
1 vote