HP-UX Reference (11i v2 07/12) - 1M System Administration Commands A-M (vol 3)

k
kctune(1M) kctune(1M)
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 infor-
mation 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 arguments
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 expres-
sion 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 evaluates to a negative
quantity will have unpredictable results.
The expression may make use of the names of other tunables. (Some tunables can-
not be used in expressions.) 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.
Expressions are evaluated only when one of the KC commands is running. If a
tunable’s value changes under other circumstances, these expressions are not re-
evaluated and the tunable values dependent on those expressions are not updated.
For example, this can happen when tunables are changed using a direct call to set-
tune(2) or settune_txn(2), or when a tunable is reset to its default value during boot
because of a validation failure.
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 con-
stants 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 when-
ever 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.
HP-UX 11i Version 2: December 2007 Update − 2 − Hewlett-Packard Company 433