What are you trying to change it from, what OS, multipathing software ?

In my experience these type of changes (array commpath, failover mode) always required host system reboot. I would shutdown the system, change whatever setting you are trying to change and bring the host back online.

Please note changing the ArrayCommPath setting can have other repercussions.

For example the ArrayCommPath setting needs to be set to 1 or enabled for PowerPath multipathing. Changing this to 0 can cause PowerPath to not be able to see devices.

If you want to remove the LUNZ devices the easiest way would be to remove the lowest LUN device from the storage group and then reassign it to the storage group specifying a HLU (Host Lun Address) of 0. This would cause the LUN to override the LUNZ device.

KB solution: emc99467 is a great start as to what the initiator settings should be per OS and more info.. Any failover mode change should be done with downtime planned and requires a host reboot (emc149420). Also, emc107962 explains about arraycommpath and a reboot is needed here as well (emc191533)