I noticed that whenever I run ocean using the -nograph option, Cadence starts a "null" X server as described in the following link.
I was wondering if there is any way to prevent Cadence from starting X server when running ocean. I am trying to run a bunch of ocean jobs at the same time in multiple compute nodes that do that support graphical modes. The problem is that I can't run ocean in these compute nodes because it wants to start an X server. It's very difficult for me to change these compute nodes to support graphics since these nodes are meant to run batch jobs that do not require graphics. Any help is appreciated in solving this. Thank you very much.
In releases from IC614 onwards, it starts a vnc server (cdsXvnc), whilst with earlier versions it runs Xndx. Both have the same objective - to be an X server with no display - to effectively swallow the graphics produced by the application. You do not get one cdsXvnc/Xndx per "-nograph" session; they are shared between multiple sessions and will automatically exit when nothing is connected.
I cannot see why you can't start ocean on a "compute node" - there is no need to support "graphical modes" (whatever that means) - no graphics are actually produced - as I said, it's a null X server intended to consume any X traffic without it actually drawing anything.
So the whole point of -nograph is to allow you to run in batch mode. You cannot run -nograph without somewhere for the X traffic to go to - it's generally best to let Virtuoso take care of managing that itself (although you can explicitly set the $DISPLAY to the destination of your choice.
The benefit of the way that this is done is that all code which opens windows, raises forms etc, continues to work - it's just that there's no way to interact with the form because it's a null display.
This has worked for many, many, years, and people are able to run such jobs on compute servers, so I'm surprised you cannot get it to work. Maybe you need to explain which version you're using and precisely what the problem you're seeing is?