You must remove at least one WWPN definition from the I/O group that you have specified before you can resubmit the command.
Determine whether the action is required.
If the action is required, review the current configuration to determine whether any current WWPN definitions for the I/O group that you have specified are not required. Remove at least one WWPN definition that is not required from the I/O group that you have specified, and resubmit the command.