Heap dump is always around 8G on process with 80G heap

[Sundara Mohan M]

Hi,
   I am trying to take a heap dump of java process with 80G heap with ZGC,
this is always giving me around 8G dump file.
Same application with ParallelGC running with 48G heap i am getting around
30G dump file.
I am using following command on both process and verified both process has
same no of request processed and Used memory from gc log is similar
   jcmd <pid> GC.heap_dump <filename>

1. Why is ZGC heap dump always less compared to process running with
ParallelGC?
2. Is there something i am missing?


Thanks
Sundar