If you attempt to delete a Snapshot copy and you get an error message saying that the Snapshot copy is busy and cannot be deleted, you either have a Snapshot copy that was taken of a LUN backed by another Snapshot copy or the Snapshot copy backed LUN is still connected.
If you have a Snapshot copy that was taken of a LUN backed by another Snapshot copy, you need to delete the newer Snapshot copy before the older Snapshot copy, the Snapshot copy backing the LUN, can be deleted.
To see if you have busy Snapshot copies, you can view your application event log in the Event Viewer to check for messages related to busy Snapshot copies. For more information about deleting busy Snapshot copies, see the Data ONTAP Block Access Management Guide for iSCSI and FC for your version of Data ONTAP.