During the installation of R/3 Enterprise, when you are prompted to enter the DDIC password, the installation sometimes...
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fails with the message: "FRF-00007 Unable to open RFC connection" I found a solution: You need to stop the installation and then log into SAP with the SAP user password "06071992", then change the DDIC password to whatever you want.
Once you're done, restart the installation and continue to the stage where you need to install the DDIC password, enter the changed password and the installation will continue without errors.
The only OSS note related to this was "Press the continue button" and the installation may continue, or restart the installation.