I've come across an error and I can't resolve it, the message is:
When I remember right, the JDBC drivers included in old iReport were just the free licenced (e.g. LGPL) ones. Not sure, what oracle licenced it's JDBC driver but I guess, you must include the jar to classpath (via options menu) manually.
Be aware with "modern" driver versions, as iReport is actually (kind of) "deprecated" and is just running with Java7.
A new JDBC driver by oracle could be compiled with newer java versions (>= 1.8) and will throw exceptions when used.
So you will need to copy a "old" driver compiled with JRE <= 1.7
hth + regards