Thanks for your replies,
1st) Example and class with Shared memory works fine. But API function CreateFileMapping doesn't see already opened file mapping object when class is compiled as DLL and referenced by Report. Same problem with OpenFileMapping API. I guess that Reporting service blocks memory access for custom dlls. I need to investigate more on that. Do you know something more?
2nd) Here is simplified explanation what I'm trying:
I have to make conversion rate report for user selection and to make evaluation of it by comparing company Total sales data to user selection. Total sales data is long running query which runs every week. I want to use snapshot of report as storage for Total sales data instead to keep data in temporary table. That way I don't have to write user interface for administration but admins can use Report Manager. Total sales data should be subreport of desired conversion rate report. So I need a way to return conversion rates of Total sales data (which are in subreport) back to main report.
I already have different approach, thanks to you and your Reporting book. I will use XML dataset to get Total sales data.
New question: Is it possible to make something like sql views with datasets in report?
Thanks again
Nikola