Migrate Completed Performance Documents from Rel 12 to Rel 13

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We have two production environments Rel12 and Rel 13. We have stopped using Rel 12 environment as Oracle provided us the Release 13 in a new environment. However, we have completed employee performance documents in Release 12 environment. We would like to know different solutions to bring performance related date from Rel 12 to Release 13. We cannot do PTP as both are on a different code level.

Is there a solution using HDL or something else? Thank you