Basic Tuning Ideas
Several times I have discovered database installations that have not even started basic tuning, so some basic recommendations on the first things to try may be useful. They apply to most database systems in principle, but I will use Oracle as an example, as I have watched over the shoulders of a few Oracle consultants in my time.
Increasing Buffer Sizes
Oracle uses an area of shared memory to cache data from the database so that all Oracle processes can access the cache. In old releases, the cache defaults to about 400 Kbytes, but it can be increased to be bigger than the entire data set if needed. I recommend that you increase it to at least 20%, and perhaps as much as 50% of the total RAM in a dedicated database server ...