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Protecting a Serial Terminal Port?

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The Question is:

Is there a way to disable the ability of setting Altypeahd on a terminal?
 Something in sysgen?  The worst part being the system needs to be rebooted to
 undo it.  We have an old sensitive async real-time application that does not
 work when it is enabled.
 Can you please address this for vms7.3-2 also?

The Answer is :

  The usual approach is to SET TERMINAL/[NO]TYPE_AHEAD/PERMANENT
  in the system startup, and /ALTYPEAHD to select the alternate
  (and usually larger) typeahead buffer.  Use of /PERMANENT will
  requires LOG_IO or PHY_IO; full ALL-class OpenVMS privileges.
  The mechanism used to control this (permanent) setting is
  the OpenVMS privilege, and specifically LOG_IO, PHY_IO,
  or (obviously) write access to the system startup procedures.
  Only privileged users can reset the attribute permanently.
  If the settings are changing (permanently), you will want
  to review the activities of the privileged users, and will
  potentially want to remote privileges from one or more users.
  You can also choose to explicitly protect the port against
  most (non-privileged) access, using the SET SECURITY command
  or similar.
  The OpenVMS Wizard is not aware of a problem here that would
  require a reboot, but might tend to assume that resetting the
  attribute either trips into a flow-control problem, or into
  a sequence of attempted logins.  In either case, there is
  generally no need for a reboot.
  Setting the required terminal characteristics in SYCONFIG.COM
  or SYSTARTUP_VMS.COM is the normal and recommended means for
  establishing the default settings.
  The OpenVMS Wizard is aware of no way to disable changes by
  an application that might wish to temporarily adjust the
  terminal settings.  The settings will revert on image exit,
  however.  (This access can be blocked by protecting the port
  with a protection mask or an ACL, obviously.)
  These machanisms have been in place for multiple major releases
  of OpenVMS.

answer written or last revised on ( 24-SEP-2004 )

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