settune.2 (2010 09)

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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 takes effect immediately, except in the cases noted below.

Some parameters cannot be changed without rebooting the kernel. These parameters cannot be changed

using

settune().

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() 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 is set by the kernel. The value parame-

ter to settune() is ignored.

STF_NOAUTO Sets the tunable parameter to the value and turns off any automatic tuning

done by the kernel.

The

tuneinfo2() call can give information 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.

Security Restrictions

The actions associated with this system call require the

SYSATTR privilege. Processes owned by the

superuser have this privilege. Processes owned by other users may have this privilege, depending on sys-

tem conﬁguration. See privileges (5) for more information about privileged access on systems that support

ﬁne-grained privileges.

RETURN VALUE

This function returns one of the following values:

STR_OK The value of the speciﬁed parameter has been changed.

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 the

SYSATTR privilege.

[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.

[EIO] The Kernel Registry Service was unavailable or encountered an error.

[ENOMEM] Insufﬁcient memory to accommodate the new parameter value.

HP-UX 11i Version 3: September 2010 − 1 − Hewlett-Packard Company 1

Summary of content (2 pages)

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settune(2) settune(2) NAME settune() - set the value of a kernel tunable parameter SYNOPSIS #include 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 takes effect immediately, except in the cases noted below. Some parameters cannot be changed without rebooting the kernel. These parameters cannot be changed using settune().
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settune(2) settune(2) WARNINGS 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 configuration 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.