Determining Precedence Among TASM Planned Environments - comment by carrie

Nazy,
 
Unfortunately, I can't tell you what settings would be best for you without being there on site and seeing all the workload management detail as a whole.   
 
But I can suggest that you need to keep workloads on the same tier through different planned environments.
 
I think you are looking at this correctly.  In the planned environment where you want this workload to have a high priority, give it a high allocation percent (like 30% or 50%).   In the other planned environments, give it a low allocation percent (like 2% to 5%, or even 1%).  Giving a workload on an SLG Tier a very low allocation percent is an effective way of keeping its CPU usage as low as you want.   However, if there are unused resources on the platform, and Timeshare workloads cannot use all the unused CPU, then SLG Tier workloads could end up consuming more than their allocation entitles them to.   I see that as a good thing.
 
If you want that workload to have a similar priority as Timeshare Top workloads, you might be able to figure that out if you look at the global weights of the Timeshare workloads in the System Workload Report screen of Viewpoint Workload Designer.  See the most recent Priority Scheduler Orange book (15.0/15.10) chapter on Global Weights  (chapter 9).  It tells you how to view the global weights of your workloads.  Some versions of Viewpoint do not display global weights for Timeshare access levels, but  I believe the most current Viewpoint screens do show the global weights of Timeshare workload broken out (global weights are called "% of System" in Viewpoint).  In addition, there is a blog posting on Dev X that discussed Global Weights.
 
https://developer.teradata.com/blog/carrie/2015/04/global-weights-in-sles-11-priority-scheduler
 
There is some trial and error involved in setting the allocation percent of SLG Tier workloads.  If you are in a position to pursue it and feel there would be a value, there is a group in Professional Services that can help with workload management setup or tuning (the Performance and Workload Management COE).
 
Thanks, -Carrie