SIMATIC WinCC Open Architecture Forum

According to the WinCC OA Documentation the XE Oracle releases are not supported.
For Windows the following Oracle releases can be used:
Server: 11.2.0.4, 12.1.0.1, 12.1.0.2
11.2.0.4 and 12.1.0.1 support the SE1, SE and EE Editions/Licenses.
12.1.0.2 supports the SE2 and EE Editions/Licenses.

Best Regards
Leopold Knipp
Senior Support Specialist

It seems XE causes only some issues on finding OCCI by RDBmanager (you should install oracle client package separately).
I think with a little effort you could enable this useful feature in your product.

Thank you again.
Regards.