One creative way to deal with balancing in-memory and IO operations is to develop self-adjusting algorithms. For example, if IO operations begin to slow down, then automatically adjust the algorithms for decreased IO operations. Or if there is an abundance of CPU power, then automatically shift processing to consume CPU with the intention of improving performance. This is one reason why good performance statistics are so important to Oracle. Fortunately for us, Oracle makes much of this information available to us.

An Oracle buffer is an Oracle segment's cached block. As you might expect, an Oracle buffer starts off containing the same information as in the Oracle block. A buffer's contents depend on the type of segment and whether it's a segment header block.

Figure 6-1 is just one way to model an Oracle data block. Oracle buffers are indeed cached in Oracle's buffer cache. While I will delve deeper into data blocks later in this chapter, my point here is that a buffer simply represents the block on disk. But if a block is accessed, a difference between the buffered block and the on-disk block can occur.