hpux man page for settune_txn

settune_txn(2)							System Calls Manual						    settune_txn(2)

NAME
       settune_txn() - sets the values of kernel tunable parameters in a transaction

SYNOPSIS
PARAMETERS
       version	      The version parameter should always be set to

       transaction    The  details  of	the changes are specified in an array of structures.  Each structure provides context to the changes to be
		      made to a single tunable, and contains at least the following fields, in unspecified order:
		      The name of the tunable parameter to be changed.	NULL-terminated ASCII string.

		      The value to which the tunable parameter must be set.

		      These are flags to describe this change within the transaction.  Valid flags
			     and their corresponding connotations are:

			     The current value of the tunable should be changed to the value
				    specified in the ktc_value parameter.  This is allowed for all tunables.  Setting the current value of a  tun-
				    able that the system is tuning automatically turns off the automatic tuning.

			     The tunable parameter is switched to its default
				    state.   For tunables that can be tuned by the system, the automatic tuning is turned on.  The value specified
				    in the ktc_value parameter is ignored.

       size	      The size of a structure, as understood by the caller.

       num_elements   The number of tunables that are being modified in this call.

       err_buf	      Errors or warning messages that give details about the tuning are passed back in the err_buf, which must specify an  address
		      in the caller's space.  The messages will be in English and returned as NULL-terminated ASCII strings.  A NULL string termi-
		      nates the error messages.

       err_bufsize    The parameter err_bufsize is a pointer to a variable containing the size of the err_buf buffer (in bytes).  Upon	completion
		      of  the  system call, err_bufsize will contain the size necessary for all the error and/or warning messages for the transac-
		      tion.  If this value is greater than the original err_bufsize value, the messages have been truncated to fit  into  err_buf.
		      A buffer of size 300 bytes per tunable is usually sufficient for the error buffer.

       stf_flags      A bitmask of flags governing the tunable change operation.  The following flag value is recognized:
		      Check  the  requested  changes, but do not actually make any change.  With this flag set, will return the same exit code and
		      error and warning messages as if it were actually making the change, but no change will be made.

DESCRIPTION
       This function is used to modify the values of a set of kernel tunable parameters at the same time.  Changes are made to the tunables  using
       a transactional change model using a three-phase commit where the following rules apply:

       o  None of the changes within a transaction succeed or all of the changes within a transaction succeed.	There are no in-betweens.

       o  No duplicates are allowed within a transaction, where duplicates are defined as more than one change to a tunable.

       o  There are no restrictions on the order in which the tunables need to be specified within a transaction.

       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.

       The  call can give information about whether or not changes to a parameter are allowed, or will require a reboot, or can be tuned automati-
       cally.  Some individual parameters may have specific notes regarding their behavior when changed;  see the man pages for  those	parameters
       for details.

   Security Restrictions
       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 configuration.  See privileges(5) for more information about privileged  access
       on systems that support fine-grained privileges.

RETURN VALUES
	      The values of the parameters have been changed and the new values are effective immediately.

	      The function did not complete successfully.  None of the
		     changes were applied.  The detailed error messages are in the buffer err_buf.

		     If the buffer size returned in err_bufsize is greater than the size of err_buf, there were more error messages than have been
		     returned.	To get the remaining errors, increase the size of the buffer and try again.

	      The function completed successfully, but there were
		     warning messages generated.  These warning messages are in the buffer, err_buf.

		     If the buffer size returned in err_bufsize is greater than the size of err_buf, some warning messages  were  generated  which
		     did not fit into the buffer.

ERRORS
       When the function returns the global variable errno will be set to one of the following values:
	      One or more of the specified tunables does not exist.

	      The caller does not have the
		     privilege.

	      The    version parameter is not valid.

	      One or more of the specified values within the transaction
		     are not within the acceptable range of values for the corresponding parameters.

	      At least one transaction rule was violated and hence none of the
		     changes were made.

	      The changes within the transaction could not be applied
		     immediately.

	      The combination of flags specified is invalid.

	      The number of elements specified is zero.

	      The size of a
		     structure as specified by struct_size is invalid.

	      The number of elements specified is greater than the number of
		     tunables available.

	      err_buf
		     or err_bufsize specifies an address that is inaccessible.

	      The Kernel Registry Service was either unavailable or
		     encountered an error.

	      Insufficient memory to accommodate the changes within the
		     transaction.

WARNING
       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.  Tunable changes made with are automatically logged to

       If the tunables being changed through are used in expressions that set the values of other tunables, those expressions will not be re-eval-
       uated  and  those  tunable  values will not be updated.	This behavior may change in future releases of HP-UX.  If expression evaluation is
       desired, use to set tunable values.

       Tunable changes made using may not remain effective across reboots.  This behavior may change in future releases of HP-UX.  If  persistence
       of changes across reboots is desired, use to set tunable values.

AUTHOR
       was developed by Hewlett-Packard Company.

SEE ALSO
       kctune(1M),  mk_kernel(1M),  gettune(2), settune(2), tuneinfo2(2), privileges(5), and the individual tunable parameter man pages in section
       5.

																    settune_txn(2)