HP-UX is a Unix operating system used on Hewlett Packard (HP) machines. HP-UX is also one of the operating systems that Oracle runs on.
Both Oracle 10g and Oracle 11g can run on HP-UX 11i (64-bit only). Oracle provides different base releases for PA-RISC and HP Itanium based servers.
Please note that PA-RISC is nearing the end of its life. HP will support PA-RISC servers until 2013, but already stopped selling their HP 9000 systems in 2008. Customers should start migrating to the newer Itanium-based machines.
Some users reported getting error:
Warning: Entry/Exit code is optimized. Cannot restore context (UNWIND 22)
This error occurs when Oracle unwinds to make a stack trace, AFTER there was some other error. You need to find out what caused Oracle to dump stack in the first place. Possibly an error prior to getting the above warning.