For some reason, after I was working on setting up VMWare ESXi 5.5 on my own server.   It worked for a week without any problem and then, I ran into the error on screen as below :

"no coredump target has been configured. host core dumps cannot be saved."

I really don't know what should I do with that and why it happened.  Tried to google and found many websites refer to this link -> Configuring a diagnostic coredump partition on an ESXi 5.x/6.0 host (2004299)

The question here is do I really need to create a partition for this purpose?  If I need it, it should be there already since it works without that error for a week before.  I really confused until I found another article here ->

Configuring ESXi coredump to file instead of partition (2077516)

"Configuring ESXi coredump to file instead of partition (2077516)" is a lot easier and I don't really need to do anything with partition at all.  Tested and it works.