In the TOILET past 10 M rows?

I heard from a local (Dallas) oracle reseller that performance for Oracle 7.0 running on HP 9000 series (715, 735, etc) goes down the toilet after about 10 million rows. I assume that means that we're joining 10 million rows in one table with some other larger transaction table (1:N).

Has anybody experienced such a sharp drop-off in performance? The reason I heard was that it was something to do with the indexing (perhaps you add another level to the index tree at this volume - although I think this would definitely depend on key size).

Any comments are welcome. I have no experience with oracle so please be kind.

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