oracle 觸發器實現禁止在資料庫中建立dblink ---透過觸發器實現

CREATE OR REPLACE TRIGGER no_create_dblink
BEFORE DDL ON DATABASE
BEGIN
IF ORA_SYSEVENT = 'CREATE' and ORA_DICT_OBJ_TYPE='DATABASE LINK'
THEN
RAISE_APPLICATION_ERROR (-20000, 'Cannot create the ' || ORA_DICT_OBJ_TYPE ||' named ' || ORA_DICT_OBJ_NAME ||
' as requested by ' || ORA_DICT_OBJ_OWNER ||'聯絡管理員');
END IF;
END;
/



驗證：
create public database link to_11 connect to scott identified by tiger using 'bylw';

ERROR at line 1:
ORA-00604: error occurred at recursive SQL level 1
ORA-20000: Cannot create the DATABASE LINK named TO_11 as requested by
??????????
ORA-06512: at line 4