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  man pages->Tru64 Unix man pages -> sys_attrs (5)              



NAME    [Toc]    [Back]

       sys_attrs  -  introduction  to kernel subsystem attributes
       used for configuration and tuning

DESCRIPTION    [Toc]    [Back]

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

       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 information about your options for configuring kernel

       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

       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    [Toc]    [Back]

       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 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  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 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 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
              subsets 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.

SEE ALSO    [Toc]    [Back]

       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),

       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 here.

       System Configuration and Tuning

       System Administration

       Network Administration: Connections

       Network Administration: Services

       Kernel Debugging

[ Back ]
 Similar pages
Name OS Title
sys_attrs_ipc Tru64 attributes for the ipc kernel subsystem
sys_attrs_cm Tru64 system attributes for the cm kernel subsystem
sys_attrs_vm Tru64 system attributes for the vm kernel subsystem
sys_attrs_vfs Tru64 system attributes for the vfs kernel subsystem
dxkerneltuner Tru64 Modifies or displays kernel subsystem attributes
sys_attrs_generic Tru64 system attributes for the generic kernel subsystem
sys_attrs_proc Tru64 system attributes for the proc kernel subsystem
sysconfig Tru64 Maintains the kernel subsystem configuration
kconfig HP-UX introduction to kernel configuration commands
sys_attrs_alt Tru64 alt subsystem attributes
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