Tuning a Solaris System

The Solaris OS is a multi-threaded, scalable UNIX^® operating system that runs on SPARC and x86 processors. It is self-adjusting to system load and demands minimal tuning. In some cases, however, tuning is necessary. This book provides details about the officially supported kernel tuning options available for the Solaris OS.

The Solaris kernel is composed of a core portion, which is always loaded, and a number of loadable modules that are loaded as references are made to them. Many variables referred to in the kernel portion of this guide are in the core portion. However, a few variables are located in loadable modules.

A key consideration in system tuning is that setting system parameters (or system variables) is often the least effective action that can be done to improve performance. Changing the behavior of the application is generally the most effective tuning aid available. Adding more physical memory and balancing disk I/O patterns are also useful. In a few rare cases, changing one of the variables described in this guide will have a substantial effect on system performance.

Remember that one system's /etc/system settings might not be applicable, either wholly or in part, to another system's environment. Carefully consider the values in the file with respect to the environment in which they will be applied. Make sure that you understand the behavior of a system before attempting to apply changes to the system variables that are described here.

We recommend that you start with an empty /etc/system file when moving to a new Solaris release. As a first step, add only those tunables that are required by in-house or third-party applications. Any tunables that involve System V IPC (semaphores, shared memory, and message queues) have been modified in the Solaris 10 release and should be changed in your environment. For more information, see System V IPC Configuration. After baseline testing has been established, evaluate system performance to determine if additional tunable settings are required.

Caution - The tunable parameters described in this book can and do change from Solaris release to Solaris release. Publication of these tunable parameters does not preclude changes to the tunable parameters and their descriptions without notice.