Thanks for your instruction.
I got singal 9 twice. It could be that someone is using memory intensive tasks during my GCSA build. I am using a shared server without workload manager like SLURM.
It is a good idea to request a dedicated server for a few weeks. It will take a least a week. See this biostar post
It would be nice if vg could save the prune arguments and then continue after an interrupt. Otherwise, it will just keep repeating the previous prune and GCSA steps.