settune(2)settune(2)NAMEsettune() - set the value of a kernel tunable parameter
This function sets the value of the kernel tunable parameter named tun‐
able to the supplied value. This new value takes effect immediately,
except in the cases noted below.
Some parameters cannot be changed without rebooting the kernel. These
parameters cannot be changed using
Some parameters represent limits on resources that can be consumed by
individual processes. In general, changes to these parameters do not
affect processes that are running at the time the change is made; they
affect only new programs started (with or an equivalent) after that
time. Some specific parameters may be exceptions to this general rule;
see the man pages for those parameters for details.
Valid values for the flags parameter and their connotations are:
The value of the tunable parameter is set by the kernel. The
value parameter to is ignored.
Sets the tunable parameter to the
value and turns off any automatic tuning done by the ker‐
The call can give information about whether or not changes to a parame‐
ter are allowed or will require a reboot. Some individual parameters
may have specific notes regarding their behavior when changed; consult
the parameter man pages for details on each specific parameter.
The actions associated with this system call require the privilege.
Processes owned by the superuser have this privilege. Processes owned
by other users may have this privilege, depending on system configura‐
tion. See privileges(5) for more information about privileged access
on systems that support fine-grained privileges.
This function returns one of the following values:
The value of the specified parameter has been changed.
The function did not complete successfully. The value of the
parameter has not been changed.
If this function returns to indicate an error, the global variable will
be set to one of the following values to indicate the error that
The specified tunable parameter does not exist.
tunable specifies an address that is inaccessible.
The caller does not have the
The specified value is not within the acceptable range for the
The value of the parameter could not be changed immediately.
The specified parameter cannot be changed without rebooting the
The Kernel Registry Service was unavailable or encountered an
Insufficient memory to accommodate the new parameter value.
It is possible to seriously degrade system performance, or even render
a system unbootable, with incorrect tunable settings. Use care when
setting tunable values. Always have a known working kernel configura‐
tion saved as a backup; if the system fails to boot after a tunable
change, boot from that backup kernel configuration. Keep good records
of all tunable changes so that they can be reversed if they degrade
system performance. Tunable changes made with are automatically logged
If the tunable being changed through is used in expressions that set
the values of other tunables, those expressions will not be re-evalu‐
ated and those tunable values will not be updated. Note that this
behavior may change in future releases of HP-UX. If expression evalua‐
tion is desired, use to set tunable values.
Changes to parameter values made with may not remain effective across
reboots. Note that this behavior may change in future releases of HP-
UX. If persistence across reboots is desired, use to set tunable val‐
was developed by Hewlett-Packard Company.
SEE ALSOkctune(1M), mk_kernel(1M), gettune(2), tuneinfo2(2), privileges(5), and
the individual tunable parameter man pages in section 5.