Hi,
You might be running into a known defect with the JDBC third party drivers for Oracle (CLRT-79361). It's an intermittent issue that can affect different Oracle releases, not only 12c.
To workaround this, please do the following:
1. Navigate to %jaspersoft-folder%/libs/c-oracle.jar file
2. Replace the c-oracle.jar from CA PPM 14.3 $clarity/lib or $install/checkinstall/tools/lib (for the record, the CA PPM version should be 14.2 and higher)
3. Rerun the Install/Upgrade of Jaspersoft
This should work, please let me know how it goes.
Kind Regards
Nika Hadzhikidi
CA Technologies
Principal Support Engineer