I recently became SUN certified Enterprise Architect after clearing all 3 parts of SCEA. It is hard to get answers to all questions one may have regarding SCEA but SCEA forum on javaranch.com is great!! I have shared my experience here for each part to help SCEA seekers.
Part 1 is objective test (One goes to a prometric center to appear for the test). Patterns (especially J2ee design patterns) are must. You must know about common patterns like front controller, service locator, business delegate, session facade etc. And also about technologies and their pros and cons – like JPA, EJB, JSF, AJAX, JSP, Servlets, JDBC, JAX-WS etc. Most of the questions will be scenario questions and where to apply what technology and pattern. Also learn about web application security.
Part 2 (assignment) is the hard part in my view. You get an assignment from SUN, which describes the requirements in 3-4 pages. Requirement document does not answer all the questions, so one has to make assumptions and note them down in a document, which is sent to SUN with assignment. In this part, one needs to come up with design – class diagram, sequence diagrams, deployment and component diagrams. One needs to learn about infrastructure like firewalls, load balancers, protocols etc. along with detailed design. Use any UML tool (I used StarUML). Be thorough with labels, steretypes, multiplicity etc. in your diagrams. In addition one needs to write down major risks related to NFRs (non functional requirements) like Scalability, Maintainability and also write mitigation strategy for each (how you think of mitigating the risk, what actions you will take etc.).
Part 3 is extension of part 2. It is subjective test with 8 questions (One goes to prometric center to appear for the test). Candidate needs to answer questions like why he picked up one pattern/technology over another, how will his architecture support NFRs.