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Why is snapshot isolation strictly weaker than SERIALIZABLE?
Asnapshot isolation forbids any concurrent transactions
Bsnapshot isolation allows dirty reads but SERIALIZABLE does not
Csnapshot isolation requires the table to fit in memory
Dsnapshot isolation allows write-skew anomalies
Answer & Solution
Correct answer: D. snapshot isolation allows write-skew anomalies
Write skew: two transactions read overlapping rows, each writes disjoint rows based on what they read, both commit. No serial order would have allowed both to base decisions on the same starting state and then commit conflicting changes. Snapshot isolation does not check for this; SERIALIZABLE does. Snapshot isolation does NOT permit dirty reads.
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