Data required by oracle user process is loaded into buffer cache, if it is not already present in cache. Proper memory tuning is required to avoid repeated disk access for the same data. This means that there should be enough space in buffer cache to hold required data for long time. If same data is required in very short intervals then such data should be permanently pinned into memory. Oracle allows us to use multiple buffers. Using multiple buffers we can control that how long objects should be kept in memory.