A number of solutions can help to eradicate CBC issues. Before you try to resolve CBC latch issues, ensure they exist. I know this sounds strange and almost condescending, but I find many DBAs ponder implementing solutions that do not fit the problem. Figure 6-14 is what you might see if serious CBC latch contention exists.

If you're on a system earlier than Oracle Database 10g, the top wait event will be latch free, and as I detailed in Chapter 3, you will need to confirm the latching issue is the CBC latch. With Oracle Database 10g and later systems, as shown in Figure 6-14, the wait event will be latch: cache buffers chains. In most cases, the CPU subsystem will be heavily utilized and overburdened.

* Tune logical IO SQL. The CBC structure becomes stressed when the answer to the question, "Is the buffer in the buffer cache?" is nearly always "Yes!" If the answer shifts to "No, it's not in the cache," you will notice sequential or scattered reads will be the issue. So, from an application perspective, look for the SQL that performs the majority of buffer gets, that is, logical IO activity. The SQL statement or statements will be there-they must exist. Do whatever you can to reduce their logical IO consumption. This means classic SQL tuning, including indexing, as well as reducing the execution rate during the performance-critical times.