Oracle Core: Essential Internals for DBAs and Developers

REPL_AUX

The description I’ve given so far of Oracle’s use of the replacement list is incomplete. It’s not seriously wrong, and if you didn’t look closely at what’s going on you could easily think it was correct and complete, but it’s not quite right. When your session needs to find a buffer to read in a new block, Oracle doesn’t start by looking at the LRU end of the REPL_MAIN list (which is what I have been saying), but rather starts by looking at the REPL_AUX list (the auxiliary replacement list), which exists as a source of buffers that are almost certain to be immediately reusable. Because of this guarantee, your session gets a little performance benefit when it’s searching for a buffer—it won’t have to waste resources dealing with dirty ...