I need to get OCI lib working on my rhel 6.3 machine and I am experiencing some trouble with OCI headers files that can't be found. I have installed (using yum install)

oracle-instantclient11.2-basic-11.2.0.3.0-1.x86_64.rpm

because this official page it's all I need to run OCI. To test the whole thing in general I've installed sqplus64, which worked after I set export LD_LIBRARY_PATH=/usr/lib/oracle/11.2/client64/lib. Unfortunately the headers files couldn't be found after setting LD_LIBRARY_PATH. Actually I am not surprised because there is no include directory in any of these oracle paths.

So the question is: Where do I get these missing header files from? Are they actually already there and I just can find them?

Btw: I am doing this whole exercise because I want to use ROracle on my R Studio server and this R package depends on the OCI library. Once I am back in R territory the road gets much less bumpier for me.

EDIT: this documentation helped me a little further. However, I guess I found some header files now in: "/usr/include/oracle/11.2/client64". But which variable do I have to set to this location?