Thanks John. The issue was resolved by adding just calendar start date and end date to the custom table. In the semantic model extensions, using the sandbox framework to create a logical star by joining the custom fact table to the Date Gregorian Calendar dimension instead of the Common Gregorian Calendar dimension.

Thanks for your responses. I was able to resolve the issue by creating a synonym in OAX_USER for the custom schema.customtable and then use the OAX_USER synonym in the semantic model extensions. We have a requirement to load external source data each month in to FDI so taking this approach. Thanks, Veena