And again, it is very unlikely mutex waits will be the top wait event (when there is not a related mutex bug), but it occasionally does occur. So it's important to understand mutex serialization control (see Chapter 3) as well as library cache internals and diagnosis.

Oracle has an incredibly difficult challenge in managing shared pool memory. This is rather obvious by all the changes, bugs, patches, and various performance problems over the years. While that may invoke some feelings of sympathy, when faced squarely with a nasty memory management-related issue, sympathy quickly turns to anger. In this section, I will explain how the shared pool memory is managed, its management progression over the years, how memory is allocated and deallocated, how to deal with the feared 4031 error, and finally how to resolve shared pool latch contention.

In Oracle 7 and Oracle8i, shared pool memory management was performed with the help of an interesting hashing structure. If you recall our discussions on the cache buffer hash chains and the library cache hash chains, then this will make perfect sense, but there was a twist.