I have heard that calling several subreports in a report causes RS to
use sequential query execution instead of parallel, but what can I do
to avoid having a large report calling 10 subreports taking 3 minutes
when each subreport individually takes <5 seconds?

The datasets for each subreport are a mixture of MDX and SQL query
strings. Each subreport takes <5 seconds to run separately, but
together called from "main" report takes 3 minutes. There are a few
parameters passed from main report to each subreport and a function or
two to translate the parameters to the appropriate format, either SQL
or MDX, to complete the dataset query strings.

Any ideas on how to optimize? Business doesn't accept 3 minutes per
report executed. We are using mostly MDX with very little SQL.

Thanks
Carrie

Is it absolutely necessary that you use subreports, instead of
including the data in a main dataset, and hiding that data in the
report?