Tunable Kernel Parameters

Tunables (or configurable kernel parameters) are kernel variables that allow the operating system to be configured to fit specific system needs, resulting in better performance and/or more efficient allocation of resources. The ideal value for each parameter is often determined by the system's particular hardware configuration, the specific mix of applications the system runs, and the trustworthiness of system users; factors that vary widely from system to system.

HP attempts to provide reasonable default parameter settings, but it may be necessary or beneficial to modify these settings to better suit the needs of your particular system's users. Refer to the individual manpage to obtain detailed information about any configurable kernel parameter.

Individual parameters usually pertain to a specific subsystem; some are independent, but others are interrelated or interact with each other. The parameter descriptions are grouped according to subsystem in “Tunables by Subsystem”.

	CAUTION: Changing kernel parameters to improper or inappropriate values or combinations of values can cause data loss, system panics, and other (possibly very obscure and/or difficult to diagnose) operating anomalies. Read the documentation. Before altering the value of any configurable kernel parameter, be sure you know the implications of making the change. Keep records. Write down the parameter name and its old value as well as the new value in case you need to restore the old value. Check ranges. Never set any system parameter to a value outside the allowable range for the parameter. (SAM refuses to store values outside the allowable range.) Be aware of side effects. Many parameters interact, and their values must be selected in a balanced way.

	IMPORTANT: All HP-UX tunable kernel parameters are release-specific. They may be added, removed, or have their meanings changed in future releases of HP-UX. The tunable parameters described in this manual are specific to HP-UX Release 11i Version 1.6. Though most of the names are the same as those in the previous releases, the behavior of specific tunables may differ significantly from previous releases. As technological advances expand system size and capabilities, it is not uncommon for maximum and/or default values of certain parameters to change between releases or to vary between 32-bit and 64-bit processors. The information provided in this manual is believed to be accurate as of the time it was written. However, system changes may occasionally result in differences between this manual and what is actually present on your system.