Hi James,
Yes I am referring to the SAP Oracle upgrade guide, page 18 section 3.6.3 Checking the Software Installation Prerequisites and page 19 section 3.6.4 Installing the New Oracle Database 12c Software.
It refers to a SAP Note 1915301 - Database Software 12.1.0.2 Installation on Unix with respect to further options. It also states that if the environment variable for ORACLE_BASE is not set to /oracle/<DBSID> use option -oracle_base /oracle/<DBSID>.
I should probably mention we are running AIX 6.1 TL 9 SP4 (6100-09-04-1441)
Cheers
Craig