Sometime ago I came here to obtain some guidance about what are useful resources, guide and topics that I should study looking for pass 1Z0-898 exam. I would like to share my experience as I think this will be helpful for other people preparing to takes this exam.
1. Absolutely read and fully understand the Pro JPA 2: Mastering the Java™ Persistence API, Mike Keith (Author), Merrick Schincariol (Author) this book is a must, read once to gain full knowledge about the concepts and then return to the part that you need to read with more detail.
2. This exam I think will be passed with great score reading and fully understand the specs. JSR 317: JavaTM Persistence API, Version 2.0, consider this after read the first book because the description of the topics are not very well but give to you a lot of statements that will appear in the exam.
3. This is not commonly said but JSR 318: Enterprise JavaBeansTM,Version 3.1EJB chapters 13 and 14 need to be read and fully understood, also good knowledge in EJB basics are welcome for this exam, you will see question in the exam talking about java.rmi.RemoteException, javax.ejb.EJBException, a lot of question that reference to stateful, stateless. I don't see nothing about MDB but consider read the section as well.
4. Answering question in StackOverflow this will give me a lot of real experience in how apply the knowledge that I learned and put me in the top answerer of the month =), before a guy that is really amazing in the jpa knowledge.
I take two months and a half preparing for this exam, more or less 1 or 2 hours per day, some exercises about CriteriaQuery, JPQL and mappings . I have a good ones that I planned to put in github later.
5. Finally after you think you will be ready for the exam, takes ethuware exams are very closed to the real exam and prepare you for a kind of tricky details that you need to be aware.
Be prepare for a lot of question of JPQL and Criteria, be prepare for really memorize Cache stuff, transactions (CMT, BMT) and a lot of questions about EM and Persistence Context, memorize the PersistenceException and its sub classes be sure to know what make tx marked for rollback. Take in mind that Locking is a topic with several question. Study very well AssociationOverride and AttributeOverride this is a must.
I think this exam is more light than Web Component but don't rely on.