The terminology is confusing. A review:
| Term |
Category |
Characterization |
| SERIALIZABLE |
A standard
isolation level |
Execution of a set of transactions must be equivalent to some serial execution of the same transactions. |
Snapshot Isolation
(SI) |
A non-standard
isolation level |
Initially believed to be SERIALIZABLE.
Convenient to implement in MVCC systems.
Subject to write skew and similar anomalies.
|
Serializable Snapshot Isolation
(SSI) |
An implementation of the SERIALIZABLE isolation level |
Truly SERIALIZABLE.
MVCC with some additional book-keeping to abort transactions at risk for
causing anomalies.
|