Scheduler Jobs - Error!!!

When trying to execute a scheduled job you may get below error sometimes in Oracle EM. ERROR

java.sql.SQLException: ORA-02800: Requests timed out ORA-06512: at "SYS.DBMS_ISCHED", line 150 ORA-06512: at "SYS.DBMS_SCHEDULER", line 441 ORA-06512: at line 2 


This is a bug in Oracle. Most of the times, restarting Oracle database may fix the issue.
Basically, an existing bug needs the oracle database restarts in a regular basis.
Restarting oracle database will flushes the database buffer cache.