edited by
1,409 views
1 votes
1 votes
is this is cascadeless?

r1(X),w2(X),w1(X), abort2, commit1
edited by

5 Answers

0 votes
0 votes
it's Cascading aborts not cascadeless because if Transaction T1 is fail before w1(x) then due to failure happened  in T1 .. Transaction T2 is also going to Rollback
0 votes
0 votes

Its a cascading rollback. As you can see in the table given below, both the transactions are working only on a single data item i.e., 'X' throughout.

Now in line-2, when T2 writes a value of data item X, then it associates itself with that data item. Now it becomes responsible for what would be the final value of X till line-2.

Moving further we see that in line-3, even transaction T1 writes a value of the data item X, thereby associating itself too with that data item.

Now these writes performed by T1 and T2 are called as Blind Writes because they wrote without reading the value of X.

This schedule is cascading rollback because T1 is dependent on T2 and since an 'abort' in T2 is taking place before committing the value of X therefore T1 would also be rolled back to maintain the consistency of the value of X.

0 votes
0 votes
T1 T2

R(X)
 

W(X)

commit

 

W(X)

abort

 

here when T2 rollbacks, T1 will be rollbacked too because it hasn't committed before T2 has been aborted. hence, there is cascading rollback. also the schedule is recoverable

 

Related questions

1 votes
1 votes
1 answer
1
budhu asked Jan 29, 2018
1,467 views
The given schedule:R1 (A) R2 (B) W2 (B) W1(A) W2 (A) Commit2 R1 (C)is revoreable, cascadeless or strict?
2 votes
2 votes
2 answers
2
6 votes
6 votes
1 answer
3
Himanshu1 asked Dec 23, 2015
1,864 views
Consider the following Two Transactions.How many Cascadeless schedules are possible over $T1$ & $T2$ ?$32$ $42$ $51$ $52$