Logging Last Resource Optimization for Distributed Transactions in Oracle WebLogic Server

摘要

State-of-the-art OLTP systems execute distributed transactions using XA-2PC protocol, a presumed-abort variant of the Two-Phase Commit (2PC) protocol. While the XA specification provides for the Read-Only and 1PC optimizations of 2PC, it does not deal with another important optimization, coined Nested 2PC. In this paper, we describe the Logging Last Resource (LLR) optimization in Oracle WebLogic Server (WLS). It adapts and improves the Nested 2PC optimization to/for the Java Enterprise Edition (JEE) environment. It allows reducing the number of forced (synchronous) writes and the number of exchanged messages when executing distributed transactions that span multiple transactional resources including a SQL database integrated as a JDBC datasource. This optimization has been validated in SPECjAppServer2004 (a standard industry benchmark for JEE) and a variety of internal benchmarks. LLR has been successfully deployed by high-profile customers in mission-critical high-performance applications.