By logging in to Parallels Power Panel (or PPP), you can check the history and current resource usage of the VPS.
URL for PPP is - https://IP_ADDRESS:4643
* For Linux, login as root with its password.
* For Windows, login as Administrator with its password.
Once you are logged in, click on "Resource Alerts" from the menu in the left side of the screen.
You should see it from there the latest and previous alerts for the resources (disk, memory and CPU) of your VPS.