Failed to add two hosts with the same hostname

Problem

Adding a host fails with the message:

PD-A000008 The host you are trying to register already exists with the name your-host-name.

Explanation

The same display names are not allowed. If you don't input the display name, it is the hostname of the host instead.

Resolution

If you input the display names, make sure that the display names are different. If you don't input the display names, make sure that the host you plan to add doesn't have the same hostname as an existing host (check the hostname command on the hosts).