Most of the current AIX systems are at 4.2.0 level of the operating system. IBM has stopped supporting AIX at 4.2.0 and all new patches are provided for 4.2.1. Many new vital security patches are needed, hence the need to upgrade to 4.2.1. Also, 4.2.1 offers the ability to export "large-file" filesystems across NFS. i.e. NFS previously was not able to access >2GB files even if they were accessible locally.
All AIX systems are scheduled to be upgraded to 4.2.1 during the winter quarter break. This will be a massive effort involving approximately 200 machines.
The list of machines to be upgraded have been assigned an upgrade priority. 0 = already running 4.2.1. i.e. skipped 1-5 in increasing order of priority.. 5 = highest, 0 = lowest.