How to increase the number of DECterms in DECwindows

[Niall76]

Hi,

I want to be able to increase the number of DECterms I can open from about 20 to 30. When I click on the DECterm icon to start a new window, no new terms open when I have already about 20 open. I guess there is a limit somewhere. I can still login remotely to this machine.
I have an Alpha 1200 server running OpenVMS 7.3 with 2gb of memory.

Many thanks,

Niall

[Steven Schweda]

Try an explicit CREATE /TERMINAL command. If
you get "%LIB-F-INSEF,insufficient event
flags", then I'd also like to know of a good
way around the limit. I know nothing, but I
suspect that there is none.

The failure with no message anywhere has
annoyed me for a long time. I suspect that
the VMS workstation market is so small that
there's little hope for improvement.

> [...] about 20 open.

I think that I have 22.

[Kris Clippeleyr]

Hi,

From my archives...

$ set displ/crea/node=0/transport=local
$ define dec$decterm_duplicate_ok 1
$ define decterm_duplicate_ok 1
$ mcr decw$terminal

Above commands start a 2nd DECterm controller.

Regards,
Kris (aka Qkcl)

[John Gillings · Accepted solution]

Niall,

DECterms use an event flag cluster to communicate with the DECterm controller process. That makes the number of DECterms associated with a controller architecturally limited to at most 23 (the number of event flags available).

To get around the limit, you need to arrange to start a new DECterm controller process. Starting the controller is easy, I don't think you even need the logical names suggested by Kris. See DECwindows documentation:

1.9.9 DECterm---Restrictions and Problems This section discusses restrictions and problems related to the DECterm application.

1.9.9.1 Maximum Number of DECterm Windows
V1.2--4

A DECterm controller can create a maximum of 23 DECterm windows. This occurs because DECterm needs an event flag for each terminal window to use. There are 23 event flags that DECterm can use. (Event flag 0 and event flags 24--32 are not available for DECterm to use.)

If you need more than 23 DECterm windows, then you must create a new controller. To create a new controller, enter the following command:

$ MCR DECW$TERMINAL

Note that the window from which this command is executed cannot be used for anything else because this command does not return until the last DECterm window is closed. After starting the controller with this method, the user can create another 23 DECterm windows with the DCL command CREATE/TERMINAL.

[Steven Schweda]

> $ MCR DECW$TERMINAL

Hmmm. This seems to be pretty effective.

> Note that the window from which this
> command is executed cannot be used for
> anything else [...]

SPAWN /NOWAIT /NOTIFY /INPUT=NL: MCR DECW$TERMINAL

Aside from some annoying messages in the
parent process terminal:

X Toolkit Warning: Cannot convert string "US_LK443AA_LK" to type Int
Allocated addresses 50c000 - 50dfff with $expreg for ptd data.

Allocated addresses 5ac000 - 5adfff with $expreg for ptd data.

[...]

... this seems to work. Add /OUTPUT = NL: to
hide the messages. Of course, if you kill
this process, all its DECterms die suddenly.
Perhaps a detached process could be created
which would be harder to whack accidentally.

[Steven Schweda]

Warning! Radical concept ahead!

If punching the little Terminal icon did this
sort of thing automatically, then who'd ever
notice that there was a problem?

[John Gillings]

Steve,

>Warning! Radical concept ahead!

Agreed.

I recall implementing some code long ago to do exactly as you describe. I've forgotten the exact details, except that extra terminal controllers were started as detached processes as required.

Unfortunately, getting such obvious ideas included in released versions was (and still is) nigh on impossible.