PermGen space

Tomcat 官网对PermGen space内存溢出的解释：

Why does the memory usage increase when I redeploy a web application?

Because the Classloader (and the Class objects it loaded) cannot be recycled. They are stored in the permanent heap generation by the JVM, and when you redepoy a new class loader is created, which loads another copy of all these classes. This can cause OufOfMemoryErrors eventually.