Oracle Core: Essential Internals for DBAs and Developers

The Library Cache

If you look back to Chapter 5, Figure 5-6, the picture of a very small buffer cache with just four cache buffers chains latches, and compare it with Chapter 4, Figure 4-3, the second approximation to a picture of the library cache, you will see that there is some similarity between the two. The text associated with those figures points out that the number of library cache hash buckets per latch is amazingly high (thousands, if not tens of thousands), while the number of cache buffers chains per latch is relatively low (typically in the range 32–128). The problems of finding, filling, reading and emptying data buffers are the same as the problems of handling the library cache (and the other components that sit in the shared pool)—so ...