I need to access Oracle7 from Oracle9. I know that this is not supported by Oracle. But, I need to find a work around. Is there one? Would using an Oracle8 instance as a bridge between 7 and 9 work? Are there any other work arounds?
You are correct that this is not supported. I have seen some people use and Oracle8i database as a bridge. They simply create a database link from the Oracle7 database to the Oracle8i database. And the 8i database has a link to the Oracle9i database.
So this does work. However, it is a brute force method that can add complexity to your production system and can have a high degree of risk. I personally wouldn't employ this method unless I absolutely had no choice. Instead, I would upgrade the Oracle7 database to Oracle9i.