The PA-5000 series uses an internal architecture that contains multiple dataplanes for packet processing and traffic handling.
Both the PA-5020 and PA-5050 contain two dataplanes, while the PA-5060 contains three.
In these devices, dataplane zero, or dp0 for short, functions as the master dataplane and determines which dataplane will be used as the session owner that is responsible for processing and inspection.
Certain types of traffic will always be owned by dp0, which includes ICMP, GRE, EtherIP, IPsec VPN tunnels that are terminating on the device, and predict sessions.
All other types of traffic will be load balanced internally using an algorithm that is weighted using dataplane session load. For these reasons, per-dataplane session utilization can vary, and this behavior is expected.