PID-killed what is it?

In the directory C:\Users\admin\.chia\mainnet\run I found that some of my plots are marked as PID-killed .
What does it mean and what to do to improve it?

How do you mean marked? Like renamed? Can you paste in the console text?

chia_full_node 16.05.2021 5:56 File “PID-KILLED” 1KB