HP-UX System Administrator's Guide: Configuration Management

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 changes 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
tunable values are changed. 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 document. An overview of the kernel tunables can
be found in Tunable Kernel Parameters, 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” (page 192).) For
example, to set nproc to 4300:
# kctune nproc=4300
To set a tunable to Default, either of these assignments will work. (Setting a
user-defined tunable to Default causes it to be removed.)
# kctune nproc=
# kctune nproc=Default
Assignments can use expressions, as noted above. Note that the assignment may need
to be quoted to avoid interpretation by the shell.
# kctune 'nkthread=nproc*2+100'
174 Configuring the Kernel