In fact this option does not exist in ontap 8.1. It is available only from 8.2 onwards. The reason for this is that 8.1 or earlier releases does not require that..!
Sometimes, depending on the environment, the license DB(v2 licenses, which starts from 8.2) will take some time to initialize. By that time, NFS would already have completed startup. As the result, NFS would be unable to find an installed license, and will fail to start. By setting this option "nfs.persistent.enable" to on, you can avoid this problem.
The advanced and diag privilege level commands are supposed to be issued by the customer only if asked to do so by NetApp support. This is because those commands can become dangerous to the data/configuration if not used properly. Use caution while using such commands.There is no public document that explains the "hidden" options. For other options, check the man page "man options".
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