Overview of Solaris System Tuning

This section provides overview information about the format of the tuning information in this manual. It also describes the different ways to tune a Solaris system.

• What's New in Solaris System Tuning?

• Tuning a Solaris System

• Tuning Format

• Tuning the Solaris Kernel

What's New in Solaris System Tuning?

The following table lists important new tunable parameters or changes in the Solaris 9 release.

The following parameters are new or changed but might not be identified as changed in this book's appendices. For more information, see the specific parameter information in the main topic chapter:

• pages_pp_maximum

• ufs_LW and ufs_HW

• md_mirror:md_resync_bufsz (new to the Solaris release)

• tcp_deferred_ack_interval

• tcp_local_dack_interval (new)

• tcp_deferred_acks_max

• tcp_local_dacks_max (new)

• tcp_xmit_hiwat

• tcp_recv_hiwat

• tcp_time_wait_interval

• tcp_ecn_permitted (new)

Tuning a Solaris System

Solaris is a multi-threaded, scalable UNIX® operating environment running on SPARC and Intel processors. It is self-adjusting to system load and demands minimal tuning. In some cases, however, tuning is necessary. This guide provides details about the officially supported kernel tuning options available for the Solaris environment.

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 of the variables referred to in the kernel portion of this guide are in the core portion, but a few are located in loadable modules.

A key consideration in system tuning is that setting various system variables is often the least effective thing 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.

Another thing to remember is that one system's /etc/system settings might not be applicable, either wholly or in part, to another 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 described here.

Caution - The variables described here and their meanings can and do change from release to release. A release is either a Solaris Update release or a new version such as Solaris 9. Publication of these variables and their description does not preclude changes to the variables and descriptions without notice.

Tuning Format

The format for the description of each variable follows:

• Variable-Name

• Description

• Data Type

• Default

• Units

• Range

• Dynamic?

• Validation

• Implicit

• When to Change

• Commitment Level

• Change History