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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.
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