Managing Oracle Middleware ORACLE_HOME and opatch

On a test system with Oracle 11gR2 and Oracle OBIEE 11.1.1.6 running opatch gives the following error -

 OPatch version  : 11.1.0.9.0
OUI version : 11.2.0.2
The OUI version is not applicable for the current OPatch version

I have an ORACLE_HOME for the database at /u01/app/.... and an ORACLE_HOME for the middleware piece. The ORACLE_HOME for the middleware needs to be correctly set as /u01/MiddlewareLocation/oracle_common to corretly find the middleware home and not revert to the database home.

The Oracle inventory location is stored in /etc/oraInst.loc
The inventory.xml file at <inventory_loc from oraInst.loc>/ContentsXML/inventory.xml store all Oracle homes.

For Oracle Middleware OPatch download is available from support site patch 6880880 or 5912518 for standalone installs like JDeveloper and Web Logic Server 10.3.6 (Read support note 224346.1)

For running OPatch with WLS 10.3.6 unpack the 5912518 patch and copy the OPatch folder into the wls_server10.3 location.
Make sure $ORACLE_HOME is set to point to the wls_server10.3 folder and run
opatch apply -jdk /usr/local/jdk1.6 /path/to/wls_patch