A newly created data item like Z is sometimes called a phantom. From the point of view of transaction U, Z is not there at first and then appears (like a ghost). Explain with an example, how a phantom could occur when an account is deleted.
What will be an ideal response?
The point is that the insertion of a data item like Z should not be interleaved with operations on the same data item by another transaction. Suppose that we define transaction V as: aBranch.delete(“Z”) and consider the following interleavings of V and U:
Then we have a phantom because Z is there at first and then disappears. that these interleavings are not serially equivalent.
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