In OBIEE, if the report has to create based on the pivot
view using UNION of 2 or more queries then there is possibility of pivot view
grand total issue because server will compute and picks up random value shows
in the pivot view grand total.
Issue with grand totals before changes.
To overcome issue, Click on the measures column in the pivot
view edit and set aggregation rule to “SUM” instead of “default”.
After setting aggregation rule to "SUM" instead of "default" the results in pivot view Grand total calculates exactly as shown below.