npty(5)                                                             npty(5)
                          Tunable Kernel Parameters



 NAME    [Toc]    [Back]
      npty - maximum number of BSD pseudo terminals (ptys)

 VALUES    [Toc]    [Back]
    Default
      npty = 60

    Allowed Values    [Toc]    [Back]
      Minimum : 1

      Maximum : System memory size

 DESCRIPTION    [Toc]    [Back]
      npty is the number of pseudo terminal (pty) drivers that a system can
      support.  The pty driver provides support for a device-pair called a
      pseudo terminal.  A pseudo terminal is a pair of character devices, a
      master device, and a slave device.  These allow communication between
      an application process and a server process.  When sending data to pty
      devices (such as  windows), a pty device must exist for every window
      that is open at any given time.

      Using a parameter value significantly larger than the number of ptys
      is not recommended.  An excessively large value wastes kernel memory
      space.

    Who Is Expected to Change This Tunable?
      Super users.  Changes to this tunable take effect at the next reboot.

    When Should the Value of This Tunable Be Raised?
      This tunable value needs to be raised when the system runs out of
      ptys.

    What Are the Side Effects of Raising the Value?
      More system memory is used.

    When Should the Value of This Tunable Be Lowered?
      This value should be lowered when a minimal system is being created.

    What Are the Side Effects of Lowering the Value?
      The system may run out of ptys.

 WARNINGS    [Toc]    [Back]
      All HP-UX kernel tunable parameters are release specific.  This
      parameter may be removed or have its meaning changed in future
      releases of HP-UX.

      Installation of optional kernel software, from HP or other vendors,
      may cause changes to tunable parameter values.  After installation,
      some tunable parameters may no longer be at the default or recommended
      values.  For information about the effects of installation on tunable
      values, consult the documentation for the kernel software being



 Hewlett-Packard Company            - 1 -      HP-UX 11i Version 2: Sep 2004






 npty(5)                                                             npty(5)
                          Tunable Kernel Parameters



      installed. For information about optional kernel software that was
      factory installed on your system, see HP-UX Release Notes at
      http://docs.hp.com.

 AUTHOR    [Toc]    [Back]
      npty was developed by HP.

 SEE ALSO    [Toc]    [Back]
      kctune(1M), pty(7).


 Hewlett-Packard Company            - 2 -      HP-UX 11i Version 2: Sep 2004