First, I need to point out that 7.2 (7.3 imminent) is current version of SonarQube, and 6.7.5 is the current LTS. You’re going to have a hard time getting support on versions earlier than that.
That said,
there are other log files in the logs directory. As a general practice, you should always check each of them when you have a problem of unknown origin
it sounds like maybe you spun up your instance on H2 for a test and then pointed it at your Oracle DB. I applaud your switch to a production database, but your Elasticsearch indices are likely out of sync - they still think you’re on H2. The easiest thing to do is
You cannot do so. H2 database is for evaluation purpose only, and (as per massive warning displayed when it’s used) there is no way to migrate data out of it.
All in all if you initially populated data in the embedded H2 database, and now wish to migrate to an actual database, then yes you need to start from the ground up.