When you assign ONTAP ownership of an array LUN, ONTAP places persistent reservations (ownership locks) on that array LUN to identify which ONTAP system owns the LUN. If you want the array LUNs to be available for use by other types of hosts, you must remove the persistent reservations that ONTAP put on those array LUNs; some arrays do not allow you to destroy a reserved LUN if you do not remove the ownership and persistent reservations that ONTAP wrote to that LUN.

For example, the Hitachi USP storage array does not have a user command for removing persistent reservations from LUNs. If you do not remove persistent reservations through ONTAP before removing the ONTAP system from service, you must call Hitachi technical support to remove the reservations.

See the Knowledge Base article What are SCSI Reservations and SCSI Persistent Reservations