The “cache buffer chain” latch wait is normal, but high values are associated with high simultaneous buffer access, similar to a freelist shortage on an index or table segment header.
Usually latch contention for these buffer caches is due to poor disk I/O configuration. Reducing contention with these latches involves tuning the logical I/O for the associated SQL statements as well as the disk subsystem.
Another factor for latch contention with buffers chain latches could possibly be hot block contention.
Oracle Metalink Note # 163424.1 has some useful tips on tuning and identifying hot blocks within the Oracle database environment.
Latch requests come in two flavors, willing to wait and no-wait modes. In willing to wait mode, when a latch cannot be acquired, the acquiring session will go into a spin mode, attempting to acquire the latch over and over a specified number of times. After the number of spins has reached a specific threshold, the session will sleep for a specified period of time, wake up and try the latch again. Spin mode is bad, but sleep mode is worse!
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