Automating the Detection of Snapshot Isolation Anomalies

Snapshot isolation (SI) provides significantly improved concurrency over 2PL, allowing reads to be non-blocking. Unfortunately, it can also lead to non-serializable executions in general. Despite this, it is widely used, supported in many commercial databases, and is in fact the highest available level of consistency in Oracle and PostgreSQL. Sufficient conditions for detecting whether SI anomalies could occur in a given set of transactions were presented recently, and extended to necessary conditions for transactions without predicate reads. In this paper we address several issues in extending the earlier theory to practical detection/correction of anomalies. We first show how to mechanically find a set of programs which is large enough so that we ensure that all executions will be free of SI anomalies, by modifying these programs appropriately. We then address the problem of false positives, i.e., transaction programs wrongly identified as possibly leading to anomalies, and present ...

• Type: Conference
• Year: 2007
• Where: VLDB
• Authors: Sudhir Jorwekar, Alan Fekete, Krithi Ramamritham, S. Sudarshan
• Keywords: Database, VLDB 2007