Maximum Db_cache_size?

Is it good or bad to use all available (not used for other purposes, eg. shared pool or pga) RAM for buffer cache? I am talking about 32GB RAM range.

Oracle is not in-memory database but anyway - memory access is faster than disk access.
However I understand that the way(algorithms) Oracle uses RAM may have a practical turning point when adding more RAM will only slow down things.

Therefor the question is:

• is Oracle(9.2 version) better at utilizing RAM(say, 10-20GB) for buffer cache?
• or is it it is better to let file system to utilize this RAM for file cache?
• none of the above, stay with moderate RAM usage (few gigabytes for buffer cache) just because buffer cache hit ration is good(98-99%)? I would just like to point out that 1% of disk ("raw") access makes up a considerable response time, may be 50% or so.

Thank you in advance,
Laimis N.

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