how to monitor cube usage in order to add more aggregations to speed up performance

hi all:

  We have finally deployed our first Enterprise level cube to production and fact table contains roughly around 150M  records. 

We also created a measure group for distinct order purpose and works fine for us. Now, we realized that the cube is responding a tad slow when users drag order count to their excel ... 

   During design phase, I created aggregation based on over all performance (  when 20% achieved, it stopped). What I want to do now is below:

1. I want to  know the usage pattern when users are navigating this cube

2. once I know the pattern, how can I add more aggregations based on that?

thanks

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