ORA-04068: existing state of packages has been discarded

可以通过在package中引入PRAGMA SERIALLY_REUSABLE来避免

参考：http://www.rampant-books.com/t_ora_04068_existing_state_of_packages_string_discarded.htm
        http://www.dba-oracle.com/sf_ora_04068_existing_state_of_packages_string_has_been_discarded.htm