latch: cache buffers chains - Problem

Hello forum members,

I am using Oracle 11g R2, I am trying to simulate load testing using Jmeter (Apache load testing tool) . I tried concurrent 200 users to execute the same query (report) but i observed a "latch: cache buffers chains" (Timed Foreground Events) with below details :

Event Waits Time(s) Avg wait (ms) % DB time Wait Class
latch: cache buffers chains 85,303 5,561 65 43.56 Concurrency.

I understand that this is due same data block concurrent read from buffer, but i want to know how can i minimize this concurrency effect by tuning any parameter / pool ? i want to tune my DB for 200 concurrent sessions.

Thanks and regards
Sumit