Data ONTAP cannot use an array LUN presented to it by a storage array until you configure a logical relationship in Data ONTAP that identifies a specific system running Data ONTAP as the owner of the array LUN.
A storage array administrator creates array LUNs and makes them available to specified FC initiator ports of storage systems running Data ONTAP. (The process for how to do this varies among storage array vendors.) When you assign an array LUN to a system running Data ONTAP, Data ONTAP writes data to the array LUN to identify that system as the owner of the array LUN. Thereafter, Data ONTAP ensures that only the owner can write data to and read data from the array LUN.
From the perspective of Data ONTAP, this logical relationship is referred to as disk ownership because Data ONTAP considers an array LUN to be a virtual disk. From the perspective of Data ONTAP, you are assigning disks to a storage system.
An advantage of the disk ownership scheme is that you can make changes through the Data ONTAP software that, on typical hosts, must be done by reconfiguring hardware or LUN access controls. For example, through Data ONTAP you can balance the load of requests among a group of systems running Data ONTAP by moving data service from one system to another, and the process is transparent to most users. You do not need to reconfigure hardware or the LUN access controls on the storage array to change which system running Data ONTAP is the owner and, therefore, servicing data requests.
Array LUN reconfiguration, such as resizing the array LUN, must be done from the storage array. Before such activities can occur, you must release Data ONTAP ownership of the array LUN.