Use the data on the oracle server directly. Why keep copies of data on the sqlServer machine. Simply setup a DMZ and have a passthrough that will send the selects (and any updates) through to oracle. If you are not familar with a DMZ, user the search term "firewall dmz" on google. However, if you want to use the SqlServer, then have a trigger on the catalog table that will immediatly send any inserts or updates to the sqlserver through a database link.
You do not need a parachute to skydive. You only need a parachute to skydive twice.