Partial strictness in two-phase locking

Abstract

Two-phase locking is a standard method for managing concurrent transactions in database systems. In order to guarantee good recovery properties, two-phase locking should be strict, meaning that locks can be released only after the transaction's commit or abort. In this paper we show that even exclusive locks can be released immediately after the commit request has arrived, without sacrificing any important recovery properties. This optimization is especially useful if the commit operation takes much time compared with the other actions, as for main-memory databases, or if the commits are performed in batches.