In case you are planning to perform any upgrades with DBUA, double-check that the init.ora parameters after the upgrade. In a production upgrade at a client site, dbua silently changed init.ora parameter NLS_TERRITORY from GERMANY to AMERICA. It was only noticed when after the upgrade, decimal and grouping number characters were swapped, leading to application problem.

Support had to admit that it is unpublished bug 16538186 and that there is NO documentation of it anywhere at the moment.

We learned from this to double-check init.ora parameters after dbua with before upgrade parameters.