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The OCMJEA cert has 4 steps:
1. MC exam
2. design assignment drawing UML diagrams
3. essay exam defending your design in assignment
4. training (can be done anytime: before, during or after)
Currently only the v6 exam (1Z0-807) is available. The exam objectives can be found
here
The assignment and essay together have to be completed in 6 months from the register date
Training is mandatory, without it Oracle won't say you complete the cert.
There are many resources that can be used for preparing JEA cert (part 1 especially) ranging from study guides to books on specific topics. Expect lots of reading or researching if you like during your prep.
To start off, get familiar with the exam objectives