Assigns a value to a system parameter as it exists in the SYSGEN work
  area.  The SET command does not modify parameter files, the system image
  on disk, or the active system. See the WRITE command for these functions.

  Format:

    SET parameter-name value

  Example:

    SET PFCDEFAULT 20

Additional information available:

parameter-namevalueQualifiers

  Name of a system parameter.  Use the SHOW /NAMES command to obtain the
  names of all the system parameters.

  An integer value or the keyword DEFAULT; integer values must be within
  the minimum/maximum values unless DISABLE CHECKS was specified; DEFAULT
  means the default value for the parameter.

Additional information available:

/OUTPUT/STARTUP

 /OUTPUT = file-spec

  Specifies that any output from subsequent commands is to be directed to
  an output file.

 /STARTUP

  Defines the name of the command procedure to be executed when the
  system is booted.

  Format:

    SET/STARTUP file-spec

  The default startup command procedure is SYS$SYSTEM:STARTUP.COM.  The
  file specification can be a maximum of 31 characters long.