Errors will be logged at the error or warning level. If you are not seeing anything in the server log though, you could enable logging at the debug level especially for the org.teiid.CTX_CONNECTOR context.
I see nothing in the logs, but maybe there is nothing to see (because it is not an error of Teiid connecting to Oracle).
Just for understanding: What exactly is the org.teiid.CTX_CONNECTOR in contrast to the org.teiid.CONNECTOR?
Sorry I did mean org.teiid.CONNECTOR