🚀 go-pugleaf

Re:

>It would be nice if the existing 3270 terminals could be used, ideally but
>necessarily emulating VT100 terminals.  An approach requiring separate
>terminals would be fine since the department that would be accessing our
>application is going to need another terminal, or PC emulating a VT100,
>in most cases anyways

Digital Equipment Corporation has a set of products that addresses this. You
need the

DEC SNA Domain Gateway-CT

which is a IBM channel attached gateway that emulates a PU5 node. It provides
access to PLUs (ie cross domain resources / APPLIDs) that run on the VMS 
systems.

On the VMS systems you install the:

MEP VT for DEC SNA 3270 Application Services

product. This provides VT220 emulation for 3270 terminals and SNA attached PCs
emulating 3270s in the SNA network. All applications that function on a VT220 
will function through this emulator. Ie things such as ALL-IN-1, EDT, full
screen applications etc.

If you need additional information please call your local Digital sales office 
or send me a mail message.

Dave

In article <1992Nov23.161012.75@dymaxion.ns.ca> bg@dymaxion.ns.ca writes:
>We are trying to determine our options for making use of an existing
>IBM SNA network for users to access an application on a VAX to eliminate
>having to install another leased line network.  The network connects 100+
>schools so it would be expensive to duplicate.
>
>It would be nice if the existing 3270 terminals could be used, ideally but
>necessarily emulating VT100 terminals.  An approach requiring separate
>terminals would be fine since the department that would be accessing our
>application is going to need another terminal, or PC emulating a VT100,
>in most cases anyways
>
[...]  

>Dymaxion Research Ltd.,                              fax: (902)421-1267
>Halifax, Nova Scotia, Canada B3J 1R2            Internet: bg@dymaxion.ns.ca

At Sprint we're taking this approach:
   DEC Gateway-CT to physically connect the SNA & DECNET sides
   DEC's VT emulator to emulate VT terminals on IBM 3270 type terminals.

This is just about the best solution you can hope for given those restraints.
Given the inherent differences in hardware you can imagine that there are some
compromises to be made, and some problems you will have to live with.  NOTHING
can make an IBM 3270 type terminal into a VT, but these products can at least
achieve an uneasy truce.  The first obstacle to overcome will be network
mapping.  If your information Systems depts (or whatever) is as closed and
thick headed as this one, you could be in a long uphill battle.  The
second major problem is that only terminals that support EAB (extended
attribute buffers) can be used.  Any other type terminal (such as an IBM
3191, et al) will get you nowhere.  The next problem is keyboard mapping.  We
try and get around this by mapping the keyboard for one specific applications,
but this is not ideal.  Note that things like the TAB key need to be mapped
to an IBM PF-key in order to function properly.  Again this is less than
ideal and has caused much hair pulling.

Let me know if you decide to embark on this (mis)adventure and maybe I
can smooth the path a bit.
cpc@shell.portal.com
 

Re:

>At Sprint we're taking this approach:
>   DEC Gateway-CT to physically connect the SNA & DECNET sides
>   DEC's VT emulator to emulate VT terminals on IBM 3270 type terminals.
> 
>This is just about the best solution you can hope for given those restraints.

Since I'm the person responsible for the team that built and/or brought these
products to market I'd like to first say thanks for the compliment.

A relatively minor nit I'd like to give the full names for the products referred 
to above. They are:

DEC SNA Domain Gateway-VT
and
MEP VT for DEC SNA 3270 Application Services

"MEP VT" is an INTEGRATA product sold and supported by Digital Equipment 
Corporation.

Re:

>The
>second major problem is that only terminals that support EAB (extended
>attribute buffers) can be used.  Any other type terminal (such as an IBM
>3191, et al) will get you nowhere.

All 3270 terminals are supported including ones without EAB. But terminals
without EAB cannot display reverse video, underlining or blinking. This makes
some VT applications very hard to use. Eg applications that like to use
reverse video to delineate fields etc. There is a setup option:

SEND_ATTRIBUTES

that needs to be set to NO for non EAB terminals. This should be done 
automatically if you are using LOGMODE entry that correctly identifies the
terminal. Strange things will happen if it is set to YES.

Dave Garrod