Neo4j-admin import can be run multiple times?

Neo4j Graph Platform Import / Export
3

It is slowing down after loading few nodes. I have split my data files into thirty files with each 1million records. It slows down half way through whether I have 30 files, 20 file or even 1 file.

How to debug this. ?

Import starting 2020-05-14 23:15:09.255-0500
  Estimated number of nodes: 6.00 M
  Estimated number of node properties: 31.00 M
  Estimated number of relationships: 5.00 M
  Estimated number of relationship properties: 0.00 
  Estimated disk space usage: 794.5MiB
  Estimated required memory usage: 1.070GiB

(1/4) Node import 2020-05-14 23:15:09.297-0500
  Estimated number of nodes: 6.00 M
  Estimated disk space usage: 632.4MiB
  Estimated required memory usage: 1.070GiB
.......... .......... .......... .......... ..........   5% ∆1s 75ms
.......... .......... .......... .......... ..........  10% ∆204ms
.......... .......... .......... .......... ..........  15% ∆402ms
.......... .......... .......... .......... ..........  20% ∆201ms
.......... .......... .......... .......... ..........  25% ∆400ms
.......... .......... .......... .......... ..........  30% ∆1s 403ms
.......... .........- .......... .......... ..........  35% ∆200ms
.......... .......... .......... .......... ..........  40% ∆1ms
.......... .......... .......... .......... ..........  45% ∆1ms
.......... .......... .......... .......... ..........  50% ∆1s 201ms
.......... .......... .......... .......... ..........  55% ∆4s 804ms
.......... .......... .......... .......... ..........  60% ∆20s 416ms
.......... .......... .......... .......... .......

I have 100Gigs of RAM but it is hardly using any RAM and CPU is also not fully used.

Thanks