HP-UX Reference (11i v2 04/09) - 2 System Calls (vol 5)

s
settune(2) settune(2)
NAME
settune - set the value of a kernel tunable parameter
SYNOPSIS
#include <sys/dyntune.h>
int settune(const char *tunable,
uint64_t value,
unsigned int flags);
DESCRIPTION
This function sets the value of the kernel tunable parameter named tunable to the supplied value . This
new value will take effect immediately, except in the cases noted below.
Some parameters cannot be changed without rebooting the OS kernel.
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 exec (2) or an equivalent) after that time. (Some specific parame-
ters 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:
STF_DEFAULT
STF_AUTO The value of the tunable parameter will be set by the kernel. The value
parameter to settune() will be ignored.
STF_NOPENDING The changes are not held pending for the next boot. If the tunable cannot be
set without a reboot, the changes are rejected. The global variable errno is
set to [ENOTSUP].
STF_NOAUTO Sets the tunable paramater to the value and turns off any automatic tuning
done by the kernel.
The caller needs to have super-user privileges to make this call. The tuneinfo2 (2) call can give informa-
tion about whether or not changes to a parameter 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.
Persistence of Changes
Changes to parameter values made with settune() will remain effective across reboots in this release
of HP-UX. Tunable parameter values are stored in the Kernel Registry database. Each time the system
boots, it reads the parameter values from the database and restores them. Changes to parameter values
made with settune() may not remain effective across reboots in future releases of HP-UX.
RETURN VALUE
This function returns one of the following values:
STR_OK The value of the specified parameter has been changed, or will be changed at next
boot.
STR_ERROR The function did not complete successfully. The value of the specified parameter
has not been changed.
ERRORS
If this function returns
STR_ERROR to indicate an error, the global variable errno will be set to one of
the following values, to indicate the error that occurred:
[ENOENT] The specified tunable parameter does not exist.
[EFAULT] tunable specifies an address that is inaccessible.
[EPERM] The caller does not have super-user privileges.
[EINVAL] The specified value is not within the acceptable range for the specified parameter.
[EBUSY] The value of the parameter could not be changed immediately.
[ENOTSUP] The specified parameter cannot be changed without rebooting the kernel and
STF_NOPENDING flag was specified.
HP-UX 11i Version 2: September 2004 − 1 − Hewlett-Packard Company Section 2−−351