Special characters show junk in CLOB columns after upgrade to Oracle 12.2.0.1 with JDBC

Thanks to my support colleague Roland Graeff who told me about this issue at a customer today. And I consider this a pretty serious issue. It can happen that Special characters show junk in CLOB columns after upgrade to Oracle 12.2.0.1. with JDBC. This is as bad as it sounds. Roland told me about a case where the application showed weird characters instead of German umlauts (ä, ö, ü, Ä, Ö, Ü) after an upgrade from Oracle Database 12.1.0.2 to 12.2.0.1. Special characters show junk in CLOB columns after upgrade to Oracle 12.2.0.1 with JDBC Roland explained to me that…