In case anyone finds this helpful:

Microsoft SQL Reporting Services (SRS) works with DB2, but parameters
for stored PROCEDUREs do not, as It does not pull a list of them from
DB2. The problem, IIRC, is that SRS sends a query to the system
catalog, and quotes the PROCEDURE's name (as it must) but the
PROCEDURE's name is in smallcaps. Which means, unless the PROCEDURE is
CREATEd in quoted-smallcaps, SRS's query will return no parameters.

The solution someone here provided was to hack the XML manually. Using
a SELECT statement that does the equivalent of the stored PROCEDURE, it
will generate a report. Then, the XML report file can be editted adding
the two section of parameters, and changing the SELECT statement to a
CALL statement.

HTH,
B.