A developer reported an Oracle famous error ORA-00600 like the following:
java.sql.SQLException: ORA-00600: internal error code, arguments: [kclcls_2], , 
ORA-00600 is an internal error which is caught but unable to be handled by Oracle instance, the real keyword is the first argument in the message, which is kclcls_2 in this case.
General speaking, ORA-00600 broadly covers many situations, we may have no idea what's going on. Mostly, they could be bugs. Many other patterns of ORA-00600 error can be found below:
As for me, I clear the memory of both instances of a RAC system instead of restarting database to solve the error.
SQL> alter system flush shared_pool;
Maybe, we should search for a real solution later.