Consider concurrent execution of two transactions T1 and T2 in a DBMS, both of…
Consider concurrent execution of two transactions T1 and T2 in a DBMS, both of which access a data object A.
For these two transactions to not conflict on A, which one of the following must be true?
Answer: A. Both T1and T2 only read A — SolutionIn DBMS concurrency control, two operations conflict if they access the same data item and at least one of them is a write operation. There are four…
- A.
Both T1and T2 only read A
- B.
T1 reads Aand T2 writes A
- C.
T1 writes A and T2 reads A
- D.
Both T1 and T2 write A
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Correct answer: A
Solution
In DBMS concurrency control, two operations conflict if they access the same data item and at least one of them is a write operation.
There are four possible combinations of operations between two transactions T1 and T2 on object A.
Read-Read: No conflict.
Read-Write: Conflict.
Write-Read: Conflict.
Write-Write: Conflict.
Therefore, for transactions to not conflict, both must perform read operations only.