After a long period of testing last week Oracle finally certified Oracle DB 11gR2 (11.2.0.3) running on RHEL 6.2 and later releases. For details see this Flash on TechDocs.With that all current distributions (RHEL5/6, SLES10/11) for Linux on System z are certified.
There also has been a webcast covering this hosted by the zSeries Oracle Special Interest Group.