After upgrading to PPM 15.3 or higher, there are times when jobs are not executing properly. Jobs set to run immediately do not execute and instead go into the 'Scheduled' status, and jobs that are scheduled do not run even after reaching their scheduled start time.
The bg-ca.log files display the following error messages when this occurs
ERROR 2018-03-06 00:02:13,608 [Thread-6] niku.njs (clarity:admin:7969970__851A9445-9C29-4BD6-A265-9BE35024798B:none)
SQL error code: 0
Error message: [CA Clarity][Oracle JDBC Driver]Object has been closed.
Caused by: java.sql.SQLException: [CA Clarity][Oracle JDBC Driver][Oracle]ORA-00028: your session has been killed