During some recent tests with creating my own self tuning threshold I found out that once you create the self tuning threshold you cannot change the settings for the sensitivity via the gui. You can still use overrides which alter the sensitivity but the slider bar shown below is grayed out after the monitor was created.
For background before we move on, what does sensitivity mean from a self tuning threshold perspective? Kevin Holman provides great information on this which is available at: http://blogs.technet.com/kevinholman/archive/2008/03/19/self-tuning-thresholds-love-and-hate.aspx. In Kevin’s blog he details what the various slider bars mean compared to what you can set using an override as follows:
Low: Inner: 4.01 Outer: 4.51 Rule Sensitivity: 4.01
Low-Mid: Inner: 3.77 Outer: 4.27 Rule Sensitivity: 3.77
Mid: Inner: 3.29 Outer: 3.79 Rule Sensitivity: 3.29
Mid-High: Inner: 2.81 Outer: 3.31 Rule Sensitivity: 2.81
High: Inner: 2.57 Outer: 3.07 Rule Sensitivity: 2.57
So once we have created our own self tuning threshold, if we want to change the value we can either delete it and re-create it or we can use overrides to change the values. I put together the following graphic below to show what each level translates to so that you can set the matching numbers for the override.