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sys_attrs(5)							 sys_attrs(5)



NAME

  sys_attrs - introduction to kernel subsystem attributes used for configura-
  tion and tuning

DESCRIPTION

  The operating	system kernel is built from many mandatory and optional	sub-
  systems. If you are logged into the root account, the	following command
  lists	the subsystems included	in the kernel for your system:

       # /sbin/sysconfig -s

  The majority of the kernel subsystems	have sets of attributes	whose values
  control different aspects of subsystem configuration.	 You can examine the
  names, the current settings, and (if applicable) the minimum,	and maximum
  settings of attributes for a particular subsystem by using the
  /sbin/sysconfig command. The -q option followed by the subsystem name
  displays attribute names and current settings. The -Q	option followed	by
  the subsystem	name displays minimum and maximum settings and the kinds of
  operations permitted on the attribute	(Configurable (at boot time),
  Reconfigurable (at run time),	Query only). In	the Common Desktop Environ-
  ment (CDE), you can run the dxkerneltuner application	to get the same
  information.

  You can use the dxkerneltuner	application or the /sbin/sysconfig -r command
  to change attributes for a kernel subsystem. For some	subsystems, attribute
  values are best applied through a stanza-formatted file that is specified
  as an	argument to the	sysconfigdb command.

  See dxkerneltuner(8),	sysconfig(8), and sysconfigdb(8) for more information
  about	your options for configuring kernel subsystems.

  The following	subsystems must	be included when the kernel is built:

    +  Configuration Manager (cm)

    +  Generic Kernel (generic)

    +  Interprocess Communication (ipc)

    +  Process (proc)

    +  Virtual File System (vfs)

    +  Virtual Memory (vm)

  A kernel also	includes a processor-specific subsystem	whose name is an
  internal code	for a particular processor. Processor-specific subsystems
  typically have no attributes,	are not	modified directly by users, and	are
  not documented.


  Other	kernel subsystems are technically optional, although a kernel almost
  always includes quite	a few optional subsystems in order for a system	to be
  useful. For information on the attributes for	a particular subsystem,	refer
  to the reference page	for that subsystem. The	names of these reference
  pages	adhere to the format sys_attrs_subsystem-name. For example, to see
  the reference	page that lists	and describes attributes for the generic
  subsystem, you can type man sys_attrs_generic	at the system command line.

  For guidelines on changing kernel subsystem attributes to improve system
  performance, see the System Configuration and	Tuning manual. Any discussion
  about	changing attributes for	reasons	other than tuning is located in	the
  appropriate administration or	program	debugging manual.

  You can adjust some subsystem	attribute values at run	time. If so, the
  attribute descriptions mention that fact. To make it easy for	you to locate
  these	attributes when	scanning lists,	an asterisk (*)	also precedes the
  names	of these attributes.

NOTES

  When changing	kernel attributes, keep	in mind	the following points:

    +  Many attributes should not be touched.

       A relatively small number of the	attributes listed by the sysconfig
       utility or dxkerneltuner	application should actually be changed and,
       if they are changed, only as part of the	system configuration and tun-
       ing tasks done by an experienced	system or network administrator.  The
       setting of most subsystem attributes should be done indirectly through
       system and network setup	applications or	be automatically adjusted by
       the kernel. This	fact is	very important to remember because attribute
       settings	can have complex interrelationships with one another, requir-
       ing (in some cases) careful manipulation	of an entire set of attri-
       butes rather than only one.  Furthermore, default settings of some
       attributes should never be touched, except by support personnel or by
       an administrator	acting on instructions from support personnel or
       patch kit documentation.

    +  A few attributes	that are reconfigurable	at run time should not be
       modified	manually.

       Most of the attributes that are modifiable at run time have been
       implemented this	way for	ease of	system tuning. Others are modifiable
       at run time only	because	of a software requirement and should not be
       changed manually. In general, do	not change the default value of	any
       system attribute	manually unless	the system documentation or your sup-
       port representative provides directions for changing it.

    +  Attributes are volatile.

       System attributes are volatile, such that their effect, values, and
       existence can change from one release to	another. This volatility is
       related to changes in kernel algorithms that make the system more
       self-adjusting, changes in the internal buffers and queues used by
       kernel software,	the need to support new	platforms and device archi-
       tectures, and so	forth. For this	reason,	attribute settings that
       worked well on one version of the operating system or on	a different
       hardware	platform should	not be simply carried forward after a system
       upgrade.	Doing so might not deliver the results you expect and might
       even degrade system performance.	It is recommended that system
       upgrades	be tested with default attribute settings in place and then
       tuned, as necessary, according to the most current system documenta-
       tion. The best procedure	to use when tuning is to tune one subsystem
       at a time. Check	the performance	effects	of your	attribute changes in
       each subsystem before changing attributes in another subsystem.

    +  The kernel software no longer uses parameter values in the
       /usr/sys/conf/param.c file.

       Some attributes used to have corresponding parameters in	the
       /usr/sys/conf/param.c file, which system	administrators were accus-
       tomed to	editing	directly in Tru64 UNIX Version 4.0D and	prior
       releases. The operating system software changed over the	course of
       subsequent releases to reduce its reliance on /usr/sys/conf/param.c
       file. Starting with Tru64 UNIX Version 5.1A, the	/usr/sys/conf/param.c
       file is not created after subsets are installed or used during kernel
       configuration. Therefore, a param.c file	migrated from a	release	prior
       to Version 5.1A has no effect on	kernel behavior.

       Attribute names are, in some cases, different from parameter names.
       Furthermore, starting with Tru64	UNIX Version 5.1A, no attribute	names
       contain hyphens;	the names are either all letters and numbers or	con-
       tain underscores.

SEE ALSO

  Commands: dxkerneltuner(8), sysconfig(8), sysconfigdb(8)

  Others: sys_attrs_cm(5), sys_attrs_generic(5), sys_attrs_ipc(5),
  sys_attrs_proc(5), sys_attrs_vfs(5), sys_attrs_vm(5)

  This list includes only reference pages for technically required subsys-
  tems.	 The number of subsystems that can be configured in a kernel is	very
  large, so all	system attribute reference pages are not listed	here.

  System Configuration and Tuning

  System Administration

  Network Administration: Connections

  Network Administration: Services

  Kernel Debugging