Just to update this thread, I upgraded to OCUM 6.4 because of the following line in the Release Notes:
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New informational events
New informational events are sent when configuration changes occur to Volume Autosize,
Volume Autogrow, and Volume Snapshot Autodelete settings.
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Unfortunately, they neglect to say (a) that OCUM 6.4 has no mechanism by which to alert on Informational events, unlike OCUM 5.x, and (b) that this only creates an event when the configuration changes, not when an actual Autogrow event occurs. So, unfortunately I am back to square one.
If anyone from NetApp Support sees this, please add the ability to alert on Autogrow events in the next release, as is already available in 7-mode (see below).
https://kb.netapp.com/support/index?page=content&id=1011987&locale=en_US&access=s