This week I've took an OCEJPAD test and passed it with 91%. I would like to add some information about my experience.
It is hard for me to determine how long it took me to prepare for this test, since I've spent few months just reading some materials and also book Java Persistence with Jpa 2.1 by Daoqi Yang. This is a very good book, but if you want to have all of the exam topics covered you should definitely read Pro JPA 2. This is basically an unofficial study guide for this exam. Next I have to say that I already had few years hands on experience with JPA, so some of the topics were pretty straight-forward to me.
I've decided to prepare for this test thoroughly starting this year, so I've dedicated about 1 month for studying. I've read through all chapters of JPA 2 and tested my skills using brilliant Enthuware mock tests. I have also created a simple test project for testing desired topics. After going through all of the questions and scoring passable points on every test I've decided to book a test in our local test centre.
So the important steps were: