HP-UX Reference (11i v2 03/08) - 1M System Administration Commands A-M (vol 3)

k
kctune(1M) kctune(1M)
a new user-defined tunable. This tunable will not directly affect the kernel, but may be
used in expressions defining the values of other tunables. The
-u option is not needed
when changing the value of a user-defined tunable; it is needed only to create one.
To remove a user-defined tunable, set it to
default. A user-defined tunable may not be
removed if it is used in the expressions defining any other tunable values.
-v Includes verbose information about the tunable parameters in the output listing. The
information includes the name and value of the tunable, a short description, its allowed
values, its dependencies on other tunables and restrictions on when the tunable values
can be changed. Not valid in combination with
-d, -g,or-P.
Arguments
The arguments to
kctune may be any mixture of tunable queries and assignments. The arguments
must each take one of the forms listed below. No spaces are permitted within each argument. If no argu-
ments are given, kctune performs a query on all tunables (subject to the constraints of the
-D or -S
flags).
tunable The value of the tunable will be reported. No change is made.
tunable
= The tunable will be set to its default state.
tunable
=Default The tunable will be set to its default state.
tunable
=expr The tunable will be set to the specified expression. expr must be an integer
expression following the expression syntax of the C programming language. Like
in the C programming language, expression evaluation is subject to rollover,
overflow and underflow. Setting unsigned tunables to an expression that evalu-
ates to a negative quantity will have unpredictable results.
The expression may make use of any tunable name. Tunable names may be
specified in all upper case letters, for backward compatibility, but this usage is
deprecated and will be removed in a future release. Note that the argument may
need to be quoted to avoid interpretation by the shell.
tunable
+=value The tunable’s value will be increased by value. value must be an integer constant
(not an expression). C syntax for octal and hexadecimal constants is supported.
tunable
>=value The tunable’s value will be set to value , unless it is already greater. value must
be an integer constant (not an expression). C syntax for octal and hexadecimal
constants is supported. Note that the argument will probably need to be quoted
to avoid interpretation by the shell.
Default State for Tunables
The default value for a tunable is not necessarily fixed. Default values can change between HP-UX
releases, or in patches. Some tunables have default values that are re-computed at boot time, or when
there is a change to the hardware configuration of the system. Some tunables change their default values
in response to changing system workloads. (These tunables are called "Automatic" tunables and are
marked in
kctune output.)
When a tunable is set to
Default, its value is controlled by the HP-UX kernel, and will be changed
whenever the default value for the tunable is re-computed. (Specific behavior of each tunable is described
in each tunable’s man page.) HP recommends that all tunables be set to Default unless the default
value is known to be unsatisfactory.
Setting a tunable to its default value is not the same as setting it to
Default. If the current default
value of a tunable example is 4000,
kctune example=4000
will set the tunable’s value to 4000 and prevent it from changing when the default value is re-computed.
kctune example=Default
will set the tunable’s value to 4000, and automatically change it whenever the default value is re-
computed.
Developer’s Note
The layout and content of
kctune’s output may change without notice, except when -P fields is specified.
Scripts or applications that need to parse the output of kctune are expected to use the -P fields option.
Section 1M−−348 Hewlett-Packard Company − 2 − HP-UX 11i Version 2: August 2003