Multiple installation of the same version on one machine?

Hi all,

I know it sounds weird but a customer wishes that I install 8.1.7.4 again in a different directory of a Solaris 7 machine, both the binaries and the data. He thinks that something went wrong when I upgraded from 8.1.7.0 to 8.1.7.4.

Where are the pitfalls?

• Do I need a 2nd oratab and do I have to change that in the dbstart procedure? I don't want the 2nd Oracle to change the 1st Oracle's data.
• Should I use another OS userid for the 2nd Oracle? That would add some extra security, so the 2nd Oracle could not get write access to the 1st Oracle's datafiles.
• Should I use a 2nd listener?
• Other hints or pointers to docs?