There are a number of inquiries regarding support of different releases of RHEL 5 or 6 within DC-RUM.
Here is where we stand on official support for RedHat Linux in current DC-RUM release (12.0.2) and upcoming one - 12.1 GA (May 2013).
RHEL6.4 - 64 Bit works well so far wtih 12.2 AMD build 555. But i am working with the new packet capture platform from Emulex called the Endace Probe which may be different enough from a generic AMD on dedicated hardware to not be a good reference. Time will tell as its a new platform.
as it's a major release, Red Hat recommands to reinstall into 6.x.
but, if you prefer doing an upgrade, you need this doc :