Download the file from the link and install the java and other dependencies on your RHEL 6.4, i have faced the similar issue while installing AMD 12.1.x on RHEl 6.4 x64_86
Download the attached file and copy them onto some "/compuware-temp" now install the binaries using
now proceed to AMD install using the following parameter
./upgrade...... bin --install-deps-from-file /compuware-temp/RHEL (enter), this should install the dependencies. Once install, install each individual file that were download using
rpm -i "package Name.rpm"
Once all the dependencies are installed successfully. Proceed with normal AMD installation, this should work for you.