sys_attrs man page on DigitalUNIX

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sys_attrs(5)							  sys_attrs(5)

       sys_attrs  -  introduction to kernel subsystem attributes used for con‐
       figuration and tuning

       The operating system kernel is built from many mandatory	 and  optional
       subsystems. If you are logged into the root account, the following com‐
       mand 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.	 These
       attributes  reside  in the /etc/sysconfigtab database.  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
       Environment (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  dynamically	 change attributes for a kernel subsystem. For
       settings that persist across system boots, attribute values are 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	infor‐
       mation 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 Commu‐
       nication	 (ipc) Process (proc) Virtual File System (vfs) Virtual Memory

       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  sys‐
       tem  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 pre‐
       cedes the names of these attributes.

       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 tuning 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, requiring
	      (in some	cases)	careful	 manipulation  of  an  entire  set  of
	      attributes  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 manu‐

	      Most of the attributes that are modifiable at run time have been
	      implemented this way for ease of system tuning. Others are modi‐
	      fiable 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 support 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 architectures, and so forth. For this rea‐
	      son, 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 nec‐
	      essary, according to the most current system documentation.  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.
	      Some attribute names contained hyphens in previous releases  and
	      now  contain underscores.	 However, when processing an attribute
	      name, the system accepts underscores and hyphens	as  equivalent
	      characters.  The /usr/sys/conf/param.c file is obsolete.

	      Some  attributes	used  to  have corresponding parameters in the
	      /usr/sys/conf/param.c file,  which  system  administrators  were
	      accustomed  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 the
	      /usr/sys/conf/param.c file. Starting  with  Tru64	 UNIX  Version
	      5.1A,  the  /usr/sys/conf/param.c file is not created after sub‐
	      sets are installed. A /usr/sys/conf/param.c file	may  still  be
	      used  to	apply  configuration  parameters to third-party driver
	      modules that require it; however, the /etc/sysconfigtab database
	      is  now  the recommended repository for configuration and tuning
	      values that are applied to the operating system at boot time.

       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 the reference pages for technically required
       subsystems. The number of subsystems that can be configured in a kernel
       is  very	 large, so all system attribute reference pages are not listed

       System Configuration and Tuning

       System Administration

       Network Administration: Connections

       Network Administration: Services

       Kernel Debugging


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