The Log File Analysis for Oracle 11g add-on paper describes step-by-step exactly how to do what you're talking about. Using the "dbquery" command from the DB Connect app, you can generate all the reports you're talking about, without affecting your Splunk license. A report query would look something like this:
| dbquery "oradb" "select to_char(report_date,'DD-MON-YYYY HH24:MI:SS'), report_type from report_log" | timechart count by report_type
... View more