The WebLogic server logs are likely to be in log4j format. At least the ones on my WebLogic server are.
The Oracle database logs are in their own format.
You could do some work to try and massage one of the log files into the same format as the other. The question would have to be why. One of the features of Splunk is it's ability to handle different log file formats and be able to provide consolidated view onto them.
