I think you're going to find problems with RMC/RSCT versions on AIX 5.3 that will preclude most DLPAR operations. I'm going completely from memory here from several years ago when I was desperately trying to sunset some old AIX 5.3 lpars. I recall an RSCT package version change that was not backward compatible with AIX 5.3. Since RSCT/RMC is the backbone of the connectivity that enables HMC communication to the LPAR, any operation that requires an RMC connection (most of them) are going to fail.
You may be able to make it work as a completely inert partition that can only be changed with a reboot that may or may not ever come back up. You should do everything you can to avoid this. If you have a functional backlevel HMC setup now, reconsider moving the E870 to a new HMC. Once moved to a new version, there is no going back to an older HMC.
Years ago, migrating AIX 5.3 lpars to workload partitions under a newer AIX version was an option. I don't know if that is still possible given the way out of date support for AIX 5.3, but it may be worth researching if you are stuck.
------------------------------
Vincent Greene
IT Consultant
Technology Services
IBM
Vincent.Greene@ibm.comThe postings on this site are my own and don't necessarily represent IBM's positions, strategies or opinions.
------------------------------