Performance Tuning process - to flush buffer cache or not -and why.

Hi All,

I am on Oracle 11.2.0.4 on LInux. I have to often work on tuning issues and have one question about it.

As part of the tuning process I flush the shared pool and buffer cache and then rerun the query and get the timing. I guess in this situation the timings are inflated due to Physical IOs. But if we don't flush the cache the timing could be wrong due to data being in buffer. So what is the right way to do? Also many times I have to re-run the same query. Now if I don't flush buffer cache then I may get wrong times due to faster logical IOs whereas in Production data may not be in memory and