When the LRU chains become a performance issue, massive LRU chain latch contention will occur. From an Oracle algorithmic perspective, the latching issue is usually the result of server processes holding an LRU chain latch too long while searching for a free buffer. There are many interconnected reasons for this, as well as solution strategies, which I'll cover throughout this section.

When Oracle was first written, the LRU algorithm was extremely simple. Figure 6-16 shows a single LRU chain with the important standard LRU algorithm elements highlighted.

Figure 6-16. A single LRU chain with the important standard LRU algorithm aspects highlighted: the least recently used (LRU) end and the most recently used (MRU) end.