Hello
OCPJP 6 is revised version of SCJP 6, as i know there is no difference between these two.
OCPJP 7 is new version from Oracle. it provides two exams first is OCAJP7, if you clear this than you are eligible for OCPJP7 or clear any certification(like OCPJP6) than also you eligible for OCPJP 7.
for syllabus you can see this link
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