I researched by it seems the exam for Oracle 12 has lack of supporting books/mock exams out there.
This is what I found so far:
practice test 1Z0-071 - Oracle Database SQL (OCA) Practice Exam
1Z0-146 - Oracle Database 11g: Advanced PL/SQL (OCP)
Study Guide for 1Z0-071: Oracle Database 12c SQL (kindle)
1Z0-146: Oracle Database 11g: Advanced PL/SQL