Howto build Active Report with 2 Data Dropdown Lists triggering one DataDeck

[IceTea]

Hi all,

i'm facing a conceptional problem.

What we wanna have:

Active Report in which user can select Month & Organization Unit.

Based on this selection, one crosstab should be rendered with data based on the selected Month and selected Organization Unit.

While Organization Unit is some kind of filter based on the initial selection, Month is not. Because based on selected month we calculate previous months and so son (YTD... PY).

For now, what we did is one single DataDeck which has Level Month and Level Organization Units as Deck items.

The crosstab with report data content is inside of this DataDeck. It has separate Query with a Master-Detail-Relationship to the DataDeck Query.

This MDR links Query item for OrgUnit with the other Query item for OrgUnit. For month the Query item of DataDeck-Query links to a month-parameter, which is used to calculate in the crosstab query a member for the selected month ([Dim View].[Time].[Timedimension].[month] -> ?prm_monat?).

So far so good.

With filtered months and filteres Orgunits, the report calculates very fast (30s). While unfiltered months (4 years) and unfiltered Orgunits (13), report doesn't come back at the moment.

My question is:
Is this best practice to face our needs or do we make some big mistakes on our way?
How would you Design this Active Report ?