WWPNs identify each port on an adapter. They are used for creating an initiator group and for uniquely identifying a storage system's HBA target ports.
The WWPNs of the host’s HBAs are used to create an initiator group (igroup). An igroup is used to control host access to specific LUNs. You can create an igroup by specifying a collection of WWPNs of initiators in an FC network. When you map a LUN on a storage system to an igroup, you can grant all the initiators in that group access to that LUN. If a host’s WWPN is not in an igroup that is mapped to a LUN, that host does not have access to the LUN. This means that the LUNs do not appear as disks on that host.
You can also create port sets to make a LUN visible only on specific target ports. A port set consists of a group of FC target ports. You can bind an igroup to a port set. Any host in the igroup can access the LUNs only by connecting to the target ports in the port set.
The storage system’s WWPNs uniquely identify each target port on the system. The host operating system uses the combination of the WWNN and WWPN to identify storage system adapters and host target IDs. Some operating systems require persistent binding to ensure that the LUN appears at the same target ID on the host.