when I use cloud foundry to collect dump file of java app and store to a nfs storage. it do not works. How I should do

Question

I met a problem: java app crashed with OutOfMemory. And I want to save the dump file when crashes with volume service.

I was recommended by this link. Now I have an NFS service and mounted to app as the guide does. My nfs has tag heap-dump. When I restart the app will show the log below: But in the directory nothing can be found. I think the permission is right to write. Is there something wrong with the steps?