At the same time the problem is seen, nolio_purging.log starts logging errors like:
2016-12-06 12:56:47,563 [JobToOffline-1] ERROR (com.nolio.platform.server.dataservices.services.purging.ActiveJobToOfflineMonitor:124) - Failed to verify old processes in database
java.lang.RuntimeException: org.hibernate.exception.GenericJDBCException: ORA-30036: unable to extend segment by 8 in undo tablespace 'UNDO'
This points to the UNDO tablespace being full:
Oracle doc explains in http://ora-30036.ora-code.com/ the ORA-30036:
unable to extend segment by string in undo tablespace 'string'
Cause: the specified undo tablespace has no more space available.
Action: Add more space to the undo tablespace before retrying the operation. An alternative is to wait until active transactions to commit.