We have a query that runs for 4 mins in 8i and hours! in 9i:

Looking at the explain plans, I see that there is a very expensive nested loop in 9i, where as it does a hash join in 8i.
Indexes are the same on both, but not used.

Then I noticed that in our 9i the hash_join_enabled param was set to false (it is true in 8i)...so I altered the session to true.
But it still does a nested loop.

Any ideas ? What else can I look at ? Can I force hash join some how ?