Just some other thoughts
Something else that could go wrong:
- index 1 is not available/corrupt. I don't think this is the problem as 85 seconds is than probably too less
- indexes are fragmented. Because 418 can have a lot of inserts at the end and deletes at the beginning, so indexes specialy in older versions can get imbalanced.
I think that a recreation of index 1 followed by an generating of statistics will help. As you use 7.3.4 I doubt if a reorg can be done when users try to access the table, so I advise to do this during a weekend.
If this doesn't help (sufficient) there are other things that can be investigated. These are the steps that can be done at that moment
- checking the excecution plan of the query
- checking the cost in Oracle
- change application query so that performance becomes better.
Hope this helps,
BTW: this post has been made on my personal view. My employer might not share my point of view.