Locking also occurs when a cursor is built and executed. But the perspective is different than pinning. Pins are concerned with memory being deallocated. A lock ensures an Oracle table related to a cursor is not altered during cursor creation and execution. Obviously, that could create some rather strange situations, and Oracle will not allow this to occur.

Before you can come up with good library cache performance solutions, you need to have a solid grasp of the library cache's architecture. With that knowledge, and the background presented in the previous chapters, you'll be able to grasp why a solution makes sense and the possible impact it can have.

The library cache architecture is extremely complex. The combined requirements of concurrency, relationships between objects, and fast searching really stress the architecture. I'll start at a very conceptual level of this architecture, and then methodically step down into ever increasing detail. I'll stop when the details are not particularly helpful for performance firefighting.