I have a 9672-R26-G5 Machine, running OS/390 R6 and R10 in two product LPARS. I am interested in (if it is possible) in running OS/390 R6 and z/OS 1.4 in LPARs on a G5 machine? Can I do this or am I forced to upgrade OS/390 R6 to at least OS/390 R10 before I can upgrade the R10 LPAR to z/OS 1.4?
Here are some considerations in your scenario.
1. Do the OS/390 V2.6 and V2.10 LPARs/CPUs share ANY resources, such as shared DASD? If so, your scenario will not work, since IBM provides no coexistence support (in the form of maintenance) between OS/390 V2.6 and z/OS V1.4. Coexistence support allows differing release levels to share resources despite differing control block structures, etc., that exist in the differing levels. For more information on coexistence, see the z/OS V1.4 Planning for Installation manual, at http://publibfp.boulder.ibm.com/cgi-bin/bookmgr/BOOKS/e0z2b131/5.1?DT=20021028151713
2. When you reach the point you want to upgrade the OS/390 V2.6 LPAR, you will not be able to upgrade it directly to z/OS V1.4, because IBM provides no fallback support (in the form of maintenance) between OS/390 V2.6 and z/OS V1.4. Fallback is the ability to bring up and run the new release for a while, then -- on the chance you encounter a severe error on the new release -- to fall back to the old release and run it while you work on the problem in the new release. For more information on fallback, see the z/OS V1.4 Planning for Installation manual, at http://publibfp.boulder.ibm.com/cgi-bin/bookmgr/BOOKS/e0z2b131/5.2?DT=20021028151713
3. Assuming coexistence/fallback is not an issue in your environment, and that you know that you're on your own with any code problem you encounter on your V2.6 system (since OS/390 V2.6 is no longer supported by IBM), you should be able to implement this scenario. If the system is stable and unchanging, this may be a workable solution.