In my quest to automate as much as possible i've noticed that (afaik) it isn't possible to change the tiering-minimal-cooling-days from the ontap powershell commands.
If you look at the volume options available you can see that you can change the tiering-policy using powershell by changing the $volume.VolumeCompAggrAttributes.TieringPolicy (from CLI: volume modify -volume (volume) -vserver (vserver) -tiering-policy, but you can't change the minimum cooling days there if the policy is set to auto (from cli: volume modify -volume (volume) -vserver (vserver) -tiering-minimal-cooling-days.
Ontap version: 9.7P3 powershell Toolkit: 9.7.1
Offcourse you could script it using the ssh commands from powershell (invoke-ncssh or invoke-ncsystemapi) but that still feels like a workaround instead of running it directly from powershell.
I wasn't able to find a way to do it with a native PSTK cmdlet either, for what it's worth. I would recommend doing it via Invoke-NcSsh or Invoke-NcSystemApi like you mentioned, although I agree it is not as clean as using an actual cmdlet.
Thank you for the reply, I was afraid you were going to say this. The biggest issue is that in order to use these commands you need to loop through it per volume instead of just getting the volumes within powershell and setting the value per volume. It slows down the script and it makes your script a lot less flexible.
Let's hope it will get corrected in a future release of the toolkit.