Q: If a session holds a buffer pin, can other sessions hold the cache buffers chains latch that covers this buffer? Why not? If one session holds a pin on the buffer, this session doesn't have to hold the CBC latch that covers this buffer, so other sessions can take the latch to work on other buffers (not this buffer of course). That's the whole purpose of using a buffer pin instead of the big latch. I think the design philosophy is this: Oracle wants to have finer granularity when it works on the thing it needs to work on. A pin, compared to a latch, does exactly that. It covers one buffer, while a latch covers a bunch. If the latch is taken by another session, this first session of course won't be able to take the latch when it wants it; it has to wait. When does the first session need this CBC latch again? It needs it to unpin the buffer after it finishes working on the buffer. Reference: Jonathan Lewis in his "Oracle Core Essential Internals for DBAs and Developers", p.112, describes how a session uses the CBC latch and buffer pin: 1. Get the latch. 2. Find and pin the buffer. 3. Drop the latch. 4. do something with the buffer content. 5. Get the latch. 6. Unpin the buffer. 7. Drop the latch.