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

Configuring a System
Reconfiguring the Kernel (HP-UX 11i Version 2)
Chapter 3 337
For more information on the -P option and its use by scripts or programs,
see “Parsing Command Output” on page 363, or the kconfig (5) manpage.
Interpreting Tunable Information
Looking at the sample output above, you can see that each tunable has a
name and a textual description. Each tunable is associated with a kernel
module whose name is listed in the verbose output (or in the table output
if -g is specified). Tunables can be seen and changed only if they are
associated with a module that is installed on the system (or are
user-defined). The module does not have to be in use.
When displaying tunable information for the currently running system,
kctune includes the current tunable value and the expression used to
compute it. If changes to the tunable’s value are being held for next boot,
the next boot value and expression are also shown. Verbose listings also
show the value the tunable had when the system was last booted. When
displaying tunable information for a saved configuration, kctune
displays only a current value.
Tunable values are computed integer expressions, which can refer to
other tunable values. (Circular references are not permitted.) The value
of a tunable could be 4200,or0x400,or12*1024,or4*nproc+20. Values
and expressions use the syntax of the C programming language.
Therefore, numbers can be written in decimal (256), octal (01000), or
hexadecimal (0x100). Expressions can use the following operators and
symbols:
( ) ~ ! - + * / % << >> < <= > >= & ^ | == != && || ?:
Whitespace is not permitted in any tunable expression. For backward
compatibility, tunable names used in expressions can appear in all
capitals, but this usage is discouraged and support for it will be removed
in a future release.
All kernel tunables have a default value, which is chosen by the
developer, and is shown in the verbose output. For some tunables, the
default value is fixed and never changes. For other tunables, a new
default value is chosen by the system at boot time. Still others can be
automatically tuned, which means that the default value can change
periodically while the system is running, in response to changing system
resources and needs. When a tunable is set to default, its expression is
reported as Default, as seen in the examples above. In these cases, the