Oracle latches and general Spinlocks

First of all we need to describe common background. According to Oracle® Database Concepts 11g Release 2 (11.2) latch is: “A simple, low-level serialization mechanism to protect shared data structures in the System Global Area.”

Latches and mutexes are the Oracle proprietary realizations of general spinlock concept. Later I will show that Oracle latch is one of the simplest and “obsolete” spinlock – TTS plus wait. Here I will describe where (and why) latch is placed in general spinlock theory.

10th anniversary of Steve Adams book

Famous Steve Adams book ‘Internal Oracle 8i Services for Latch, Locks and Enqueues’ was published 10 years ago on October 1999. This book founded new era of Oracle performance tuning and internals research.

The book opened for us the unknown world of Oracle Internals. Even now, after the decade it is an ultimate reference for many Oracle latch and lock related topics. For ten years we fight with the latch concurency using Steve Adams recipes. There were even rumors that this book was used inside Oracle as the manual. In particular, Oracle University Data Server Internal Seminars, has a lot of parallelism with this book. Everyone who seriously dive into this topic always should read it.

But the Oracle latch technologies were evolved greatly during the last decade! We need the contemporary knowledge.