The statement "You must take the LUN offline to enable space allocation" is incorrect. You'll probably need to restart the host to make the changes take effect, but I see no reason to offline the LUN and ONTAP does not impose this restriction.
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Page URL
https://docs.netapp.com/us-en/ontap/san-admin/enable-space-allocation.html
Page title
Enable space allocation for SAN
Summary
The statement "You must take the LUN offline to enable space allocation" is incorrect. You'll probably need to restart the host to make the changes take effect, but I see no reason to offline the LUN and ONTAP does not impose this restriction.
Public issues must not contain sensitive information