There are many problems-some would say challenges-associated with the shared pool. The constant inclusion of new memory structures, new requirements of all kinds, and highly dynamic memory management contribute to the situation.

* Intimate relationships: Shared pool objects are related and can be intimately connected with each other. For example, a single table column may be related to literally thousands of SQL statements and programmatic constructs (functions, procedures, and packages). If that one column is altered, that single change can ripple (cascade) throughout all its relationships. The result could be the invalidation of every associated object, which would force recompilation and rebuilding of cursors, and that could require massive latching, pinning, and locking of resources. As you can see, these interconnected and dynamic objects present a very difficult problem.

* Memory fragmentation: Oracle has made absolutely amazing progress in this area. Memory fragmentation used to be one of most common performance problems. But Oracle has taken a number of steps in both architecture and instance parameter flexibility, allowing us ways to influence Oracle to better adjust its behavior to a particular application's character. Throughout this chapter, notice how memory management has evolved, and how we can alter and influence Oracle's shared pool memory management.