buffer busy waits

Wait until a buffer becomes available.

There are four reasons that a session cannot pin a buffer in the buffer cache, and a separate wait event exists for each reason:

1. "buffer busy waits": A session cannot pin the buffer in the buffer cache because another session has the buffer pinned.

2. "read by other session": A session cannot pin the buffer in the buffer cache because another session is reading the buffer from disk.

3. "gc buffer busy acquire": A session cannot pin the buffer in the buffer cache because another session is reading the buffer from the cache of another instance.

4. "gc buffer busy release": A session cannot pin the buffer in the buffer cache because another session on another instance is taking the buffer from this cache into its own cache so it can pin it.

Prior to release 10.1, all four reasons were covered by "buffer busy waits." In release 10.1, the "gc buffer busy" wait event covered both the "gc buffer busy acquire" and "gc buffer busy release" wait events.

Wait Time: Normal wait time is 1 second. If the session was waiting for a buffer during the last wait, then the next wait will be 3 seconds.