HP-UX System Administrator's Guide: Configuration Management

To create a user-defined tunable, use the -u (user-defined) option when you assign
the tunable a value. The -u option is not needed to change the value of an existing
user-defined tunable.
Using the += symbol, you can increase the value of a tunable (by 100, in this example):
# kctune nproc+=100
Using the >= symbol, you can ensure a minimum value of a tunable. The command:
# kctune 'nproc>=5000'
will set nproc to 5000 if its current value is below 5000. If its current value is already
5000 or greater, it will be left unchanged. Note that the assignment is quoted to avoid
interpretation by the shell.
See the kctune(1M) manpage for details.
When you change a tunable value using a command as in the above examples, the
change will be made immediately to the currently running system, if possible. Sometimes
it’s not possible to make the change immediately; for example, you might be trying to
reduce the maximum value of some resource to below the current usage. Also, there
are some tunables that cannot be changed without a reboot. In those cases, kctune
will hold the change and apply it at next boot. If any change on the kctune command
line has to be held for next boot, they all will be.
Sometimes you may want to force a change to be held for next boot, instead of applying
it immediately. In these cases you can use the -h (hold) option of kctune to force that
behavior. HP recommends that this option be used only when the next boot is expected
to be soon. If, for example, the next boot doesn’t happen for months after making such
a change, the system administrator could be unpleasantly surprised at the effect of a
pending change that had been forgotten.
Changes to saved kernel configurations can be made by using the -c (configuration)
option. Such changes are made to the saved configuration immediately, but they won’t
affect the running system until that saved configuration is either loaded or booted. See
“Managing Saved Configurations with kconfig” (page 189) for more information.
When changing tunable values, kctune supports the -b (backup) option to specify
backup behavior, and the -C option to specify a log file comment. See “Recovering
from Errors” (page 197) and “The Kernel Configuration Log File” (page 195) for details.
Managing Kernel Tunable Parameters with HP SMH
HP SMH can be used to query and change the values of kernel tunable parameters
(“tunables”) in the currently running configuration. Using HP SMH, you can:
• Modify the value of a tunable
• View details about a tunable
• Search for a tunable
• Check the current and next boot value for a tunable
• Print details about a tunable or print a list of all tunables
Managing Kernel Tunable Parameters with HP SMH 175