preview.cmd(4)

NAME
      preview.cmd - SAM-QFS preview directives file

SYNOPSIS
     /etc/opt/SUNWsamfs/preview.cmd

AVAILABILITY
     SUNWsamfs

DESCRIPTION
     An archive or stage request for a volume that is not
     currently loaded goes to the preview area for future
     consideration.  A user can control the scheduling of preview
     requests, thus overriding the default behavior, by entering
     directives in the preview.cmd file.

     The preview.cmd file contains directives for modifying
     preview request priorities.  The directives allow users to
     increase the priority for specific VSNs and change archive
     request priorities based on the file system states regarding
     High Water Mark (HWM) and Low Water Mark (LWM).  These
     directives are read by sam-amld at start-up time, and all
     values specified are stored in shared memory.  The priority
     specifications cannot be changed while the sam-amld daemon
     is running.

     The preview.cmd file can contain comments.  A comment begins
     with a pound character (#) and extends through the end of
     the line.

DIRECTIVES
     The directives in the preview.cmd file are specified one per
     line.  With regard to their placement within the preview.cmd
     file, there are two types of directives:

     o Global directives.  These directives apply to all file
       systems.  Directives are assumed to be global if they
       appear in the preview.cmd file prior to any fs =
       directives.

     o Directives specific to a particular file system.  File
       system specific directives must appear after the global
       directives in the preview.cmd file.  A directive line with
       the following form names a specific file system and
       indicates that all subsequent directives apply only to
       that file system:

       fs = file_system_family_set_name

       A subsequent fs = directive in the preview.cmd file
       declares a set of directives that apply to another file
       system.  File system specific directives override general

       directives.

     Some directives can be used as both global and file system
     specific directives.  This can be useful, for example, if
     you want to specify the hwm_priority directive globally to
     apply to most SAM-QFS file systems but you also want to use
     it as a file system specific directive to specify a
     different value for one particular file system.

     The following sections describe the directives that can
     appear in a preview.cmd file.  You can specify either an
     integer or a floating point value as an argument to the
     _priority directives, but the system stores the value as a
     floating point value internally.

  GLOBAL DIRECTIVES
     Global directives must appear in the preview.cmd file before
     any fs = directives.  They cannot appear after an fs =
     directive.  The global directives are as follows:

     vsn_priority = value
               This directive specifies the value by which the
               priority is to increase for VSNs marked as high-
               priority VSNs.  For more information, see the
               chmed(1M) man page.  The vsn_priority = 1000.0 by
               default.

     age_priority = factor
               This global directive specifies a factor to to be
               applied to the time (in seconds) that a request is
               allowed to wait in the preview area to be
               satisfied.  The factor is as follows:

               o A factor > 1.0, increases the weight of the time
                 when calculating the total priority.

               o A factor < 1.0, decreases the weight of the time
                 when calculating the total priority.

               o A factor = 1.0 has no effect on the default
                 behavior.  The age_priority = 1.0 by default.

     For more information, see the PRIORITY CALCULATION section
     of this man page.

  FILE SYSTEM SPECIFIC DIRECTIVE
     The fs = directive specifies a particular file system and
     applies only to that specified file system.  This
     directive's syntax is as follows:

     fs = file_system_family_set_name
               This directive indicates that the subsequent

               directives apply only to the indicated
               file_system_family_set_name.

  GLOBAL OR FILE SYSTEM SPECIFIC DIRECTIVES
     Several directives can be used either globally or as file
     system specific directives.  These directives are as
     follows:

     hwm_priority = value
               This directive indicates the value by which the
               priority is to increase for archiving requests
               versus staging after the file system crosses the
               HWM level.  This means that the releaser is
               running.  The hwm_priority = 0.0 by default.

     hlwm_priority = value
               This directive indicates the value by which the
               priority is to increase for archiving requests
               versus staging.  This directive is effective when
               the file system is emptying, and the amount of
               data is between the HWM and the LWM.  Because the
               file system is emptying, you may want to give
               priority to loads for stage requests.  The
               hlwm_priority = 0.0 by default.

     lhwm_priority = value
               This directive indicates the value by which the
               priority is to increase for archiving requests
               versus staging.  This directive is effective when
               the file system is filling up, and the amount of
               data is between the HWM and the LWM.  Because the
               file system is filling up, you may want to give
               priority to loads for archive requests.  The
               lhwm_priority = 0.0 by default.

     lwm_priority = value
               This directive specifies the value by which the
               priority is to increase for archiving requests
               versus staging when the file system is below the
               LWM level.  The lwm_priority = 0.0 by default.

PRIORITY CALCULATION
     The total preview request priority is the sum of all
     priorities and is calculated as follows:

     Total priority = vsn_priority + wm_priority + age_priority *
     time_in_sec

     The wm_priority in the previous equation refers to whichever
     condition is in effect at the time, either hwm_priority,
     hlwm_priority, lhwm_priority, or lwm_priority.  All
     priorities are stored as floating point numbers.

EXAMPLES
     Example 1.  This example preview.cmd file sets both the
     vsn_priority and hwm_priority for the samfs1 file system.
     Other SAM-QFS file systems not specified here use the
     default priority for the HWM.  All file systems use the
     default priorities for the LWM and the state between LWM and
     HWM.

     vsn_priority = 1000.0
     fs = samfs1
     hwm_priority = 100.0

     Example 2.  The next example preview.cmd file sets priority
     factors for all SAM-QFS file systems, but it sets an
     explicit and different HWM priority factor for the samfs3
     file system.

     hwm_priority = 1000.0
     hlwm_priority = -200.0
     lhwm_priority = 500.0
     fs = samfs3
     hwm_priority = 200.0

SEE ALSO
     chmed(1M), sam-amld(1M).