Is it always mandatory for a review period to have a goal plan to create performance documents?

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In our last performance cycle we observed for some users performance document is not created although they are eligible for the cycle. We ran eligibility batch process with create document ' yes' option. But issue not sorted out. After that we identified there is no any goal plan assigned to them. Hence performance document is not created for them. Our performance cycle starting with Goals and performance review stage and include self evaluation and manager evaluation. Most of our users are entering goals at performance document level but not goal page. I need to know why is it requires to