Why are you looking to set this? Was it due to a prior bug?
Please open a case because we need to review those settings and those are very specific. Modifying non-publically available values without knowledge of what they do from Support/Engineering will cause system problems or unexpected situations we cannot guarantee will be safe or well functioning.
Hmm, that seems odd. I think that's more a recommendation for FAS/spinning drives than AFF. Again, while this may seem like a simple request, I'd like to get a case opened so we can give it our best watchful eye. Since I don't see your system details I cannot provide guidance.
It is a VERY GOOD idea to open a case with NetApp to track this change on your system.
Get the Current Status:
With that said, those options are set in two different locations. One is on the node (before creating the aggr) and the other is on the aggr (after setting the node option and creating the aggr)
To set the ndoe option wafl.optimize_write_once, you need to do that from the NODE SHELL.
Get the Current Status: system node run -node * options wafl.optimize_write_once
Set the option to off: system node run -node * options wafl.optimize_write_once off
***If you do not need it set on all nodes, then be sure to specify nodes instead of using "*"
To modify the Aggregate option, (first be sure the NODE option is set on all controllers that WILL contain the Exchange AGGRs), create the aggregate (GUI or CLI) and then modify it with the option change: