settune_txn man page on HP-UX

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settune_txn(2)							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  tunable  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 spec‐
		      ify an address in the caller's space.  The messages will
		      be  in  English  and  returned  as NULL-terminated ASCII
		      strings.	A NULL string terminates 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 transaction.  If this value  is
		      greater  than  the  original err_bufsize value, the mes‐
		      sages 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	opera‐
		      tion.  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 follow‐
       ing rules apply:

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

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

       ·  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 parame‐
       ter 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 configura‐
       tion.  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 val‐
	      ues 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 gen‐
		     erated 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 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
       to

       If the tunables being changed through are 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.  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), privi‐
       leges(5), and the individual tunable parameter man pages in section 5.

								settune_txn(2)
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