Finally, from an Oracle perspective, increasing the buffer cache can provide the database writer some relief from short but intense block change activity bursts. A larger buffer cache allows the cache to fill with dirty buffers, while not forcing the database to write unexpectedly, so it has more time to create larger and therefore more efficient batches. If you really want to stress a database writer, create a small buffer cache and get some DML going. You'll see the database writer frantically trying to rid the tiny buffer cache of dirty buffers.

From an operating perspective, there should be an IO bottleneck. While rare, if write caching is working wonderfully with IO write response times less than 5 ms, the total write time could be large enough to push, say db file parallel write, to the top. When this occurs, focusing on the IO subsystem will likely have little substantial effect. In this situation, focus on reducing the application IO write activity and increasing Oracle write efficiency. This also means creatively reducing write activity during peak database activity. Experienced DBAs have seen write-intensive IO activity like RMAN, backups and file transfers being performed during normal business hours. Decreasing non-Oracle IO requirements effectively increases the IO subsystem's capacity.

The wait event free buffer waits is closely related to database writer activity and is usually seen with the wait events db file parallel write and log file parallel write (log writer writing). Yet the free buffer waits event is unique in that it takes an interesting combination of database writer, IO subsystem, and server process activity to manifest.