As usual there are the release notes and the technical notes in two separate documents. The complete documentation can be reached from the Red Hat documentation page (you need to select "6" on the left bar).
For System z this has been a mainly a fix release. Only a few small enhancements have been added all described in the technical notes. Here are some of them:
- s390utils update
- crypto updates: libica, opencryptoki (including EP11 support)