Red Hat has announced the availability of RHEL 6.3. The kernel level is now kernel-2.6.32-279.el6, for the main bug fixes see the kernel update description.
As usual there are the release notes and the technical notes in two separate documents. The focus of this release has again been bug fixing. So a lot of fixes and minor enhancements especially in the s390utils have been delivered.
The IBM documentation for RHEL 6.3 for System z is on developerworks.
(update 8/15/2012)
If you are experiencing problems with accounting CPU time on RHEL 6.3 on System z, please upgrade to kernel 2.6.32-279.5.1.el6.s390x. This contains a very important fix for System z.