One item on my PerformancePoint wish list is the ability to change a datasource for an Analytic Chart/Grid. There is no way to do this. Instead you must create a new datasource and build the Analytic Charts/Grids from scratch using the new datasource. Why would someone want to change the datasource of an Analytic Chart/Grid? Well, here is what happened to me recently: A bunch of Analytic Charts were using the same datasource, and I had a request to limit the “drill down to” for a certain half of the Analytic Charts to just a couple of dimensions, as opposed to the couple dozen dimensions being shown. So, I created a perspective in the cube that limited the visible dimensions to those couple of dimensions. But then the problem crept up: if I changed the datasource to use this new perspective, then all Analytic Charts that use this datassource would be changed to have just the couple of dimensions visible. But I only wanted half the Analytic Charts to change. So then I decided to create a new datasource that used the new perspective, then went to change half the Analytic Charts to use this new datasource. But no luck – there is not a way to do that.
Note: Scorecards have the option to change the data source, but that ability was never given to Analytic Charts/Grids.
Bottom line: Use different data sources for groups of Analytic Charts/Grids if you think down the road you will want to use different perspectives for each group.
UPDATE: I have not tried it, but this appears to solve the problem via API calls: PerformancePoin