Managing Systems and Workgroups: A Guide for HP-UX System Administrators

Configuring a System
Reconfiguring the Kernel (HP-UX 11i Version 2)
Chapter 3338
system is free to choose the value it thinks optimal, and to change it as
needed. HP recommends that tunables be left set to default unless the
default is known to be unsatisfactory.
Note: setting a tunable to Default is not the same thing as setting it
explicitly to the default value reported by kctune. Using the example
above, if you set nproc to 4200, its value will remain 4200 until you
change it. However, if you set nproc to Default, its value will be kept up
to date with any improvements HP makes to the default value for nproc.
Some tunables have constraints on their values, which are shown in the
verbose output. Sometimes these are minimum and/or maximum values,
as shown for nproc above. Other times these are fixed relationships
between tunables (for example, acctresume must be greater than
acctsuspend) or restrictions on the allowed values (for example,
dnlc_hash_locks must be a power of two). These constraints are
enforced whenever changing tunable values. There are other constraints,
not shown by kctune, that are based on the current state of the system
and can change over time (for example, nproc cannot be set to less than
the number of processes currently running). These constraints are
enforced only when changing the currently running system, and not
when making changes held for use at next boot or changes to a saved
configuration.
Some tunables have restrictions on when their values can be changed.
These restrictions are noted in the kctune output. Tunables whose
values can be changed immediately are marked Immed. Tunables whose
values can be automatically tuned by the system are marked Auto.
Tunables without either marking can only be changed with a reboot.
All HP-UX tunables have manpages. To obtain information about the
behavior, allowed values, and side effects of a tunable, consult the
manpage for that tunable, which can be found in section 5 of the online
manual. An overview of all of the kernel tunables can be found in the
Tunable Kernel Parameters document, available on
http://docs.hp.com.
Changing Tunable Values
To change the value of a tunable, put tunable value assignments on the
kctune command line. (Or see “Managing Configurations with System
Files” on page 356.) For example, to set nproc to 4300:
# kctune nproc=4300