DB Buffer Cache Size

This is a silly question.

Is there a point where the DB Buffer Cache can be sized too large? One of the Oracle "luminaries" (who will remain nameless in this post) I used to speak with was somewhat adamant that proper SQL tuning, data placement, and SGA tuning would thus result in a reduction in the size of the data cache. He would maintain that Oracle9i's new features (such as PGA_AGGREGATE_TARGET, WORKAREA_SIZE_POLICY, V$DB_CACHE_ADVICE, an entire Oracle SGA can be kept to a minimum, workable size.

Okay, maybe I am simplifying the case a bit. What got me to thinking about this was the way a customer had his instance configured. This was an Oracle 8.1.7.4 database, with over 5 terabytes of online storage. The SGA had been configured with several gigabytes of data cache. As I understand it, this is a financial system, not OLTP. I was just wondering if perhaps the database had been OVER-sized due to the perception that so much data would be better handled by a large buffer cache.

I am interested in hearing experts' opinions pro or con or otherwise on this question. TIA.

Fred

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