The Robustness Problem for Database Transactions

Transaction processing is a central part of most database applications. While serializability remains the gold standard for desirable transactional semantics, many database systems offer improved transaction throughput at the expense of introducing potential anomalies through the choice of a lower isolation level. Transactions are often not arbitrary but are constrained by a set of transaction programs defined at the application level (as is the case for TPC-C for instance), implying that not every potential anomaly can effectively be realized. The question central to this talk is the following: when - within the context of specific transaction programs - do isolation levels weaker than serializability, provide the same guarantees as serializability? We refer to the latter as the robustness problem. This talk surveys recent results on robustness testing against various isolation levels.