What happens if you rewrite the view to not use the OPEN Query?
CREATE VIEW dah_test AS
SELECT semester, count(*) as reg
GROUP BY semester
(You will need to put the correct Oracle schema in place for this to work.)
With the way that you have it written then entire table will be transferred from the Oracle server to the SQL Server, then the SQL Server will do the GROUP BY and COUNT operation. This way the Oracle server does the work, and simply returns you the information that you need.
It could simply be that you need to include the Schema in your OPEN Query as well.