SQL> exec dbms_output.put_line(sqlerrm(-12528));
ORA-12528: TNS:listener: all appropriate instances are blocking new connections

PL/SQL procedure successfully completed.

CREATE OR REPLACE TRIGGER SYSTEM.TRG_SENDALARM
BEFORE INSERT
ON SYSTEM.MYVW_SENDALARM 
REFERENCING NEW AS NEW OLD AS OLD
FOR EACH ROW
DECLARE                                                                                                                                     
           V_NODE         VARCHAR2(50);           -- node name
           V_NAME         VARCHAR2(50);           -- database/host/listener name
           V_TYPE         VARCHAR2(20);           -- type of failure
           V_SEV          VARCHAR2(10);           -- severity level
           V_STATUS       VARCHAR2(30);           -- event UpDown
           UpDowntime     VARCHAR2(30);           -- timestamp long format
           v_SendAlarm    VARCHAR2(2000);
           V_CODE         VARCHAR2(20);           -- output, databae, rac or listener
           Blackout       VARCHAR2(30);           -- blackout period 9pm - 7am
           V_OPAS_LEVEL   NUMBER;
           V_ACTIVE_NODE  VARCHAR2(1); 
    BEGIN
           -- Don't have to check if databases are in the monitored list because they 
           -- have been filtered out in the view SYSMAN.OEMALERT_VIEW 
         V_STATUS := :NEW.CURRENT_STATUS;
         UpDowntime := TO_CHAR(SYSDATE,'MON-DD-YYYY HH12:MI:SS AM');
         Blackout := TO_CHAR(SYSDATE,'HH24:MI:SS');
    IF :NEW.CURRENT_STATUS=0 -- db/listener/host down
         THEN 
         SELECT DISTINCT TARGET_NAME INTO V_NAME FROM SYSMAN.OEMALERT_VIEW
          WHERE TARGET_GUID=:NEW.TARGET_GUID;
         SELECT DISTINCT TARGET_TYPE INTO V_TYPE FROM SYSMAN.OEMALERT_VIEW
          WHERE TARGET_GUID=:NEW.TARGET_GUID;
         SELECT DISTINCT HOST_NAME INTO V_NODE FROM SYSMAN.OEMALERT_VIEW
          WHERE TARGET_GUID=:NEW.TARGET_GUID;         
            V_STATUS:='Target Down';
         SELECT OPAS_LEVEL , ALERT_ACTIVE INTO v_OPAS_LEVEL, V_ACTIVE_NODE FROM SYSMAN.SENDALARM_NODES
          WHERE UPPER(NODE_NAME) like UPPER(V_NODE||'%');   
         -- Decide type of output, databae, rac, listener or host     
            CASE
                WHEN V_TYPE = 'host'                THEN    V_CODE:=V_NAME;
                WHEN V_TYPE = 'oracle_database'     THEN    V_CODE:=UPPER(V_NAME);
                WHEN V_TYPE = 'rac_database'        THEN    V_CODE:=UPPER(V_NAME);
                WHEN V_TYPE = 'oracle_listener'     THEN    V_CODE:=UPPER(SUBSTR(V_NAME,1,8));
            END CASE;
           -- blackout for SEV3 between 9PM-7AM
           DBMS_OUTPUT.PUT_LINE(BLACKOUT);
           IF  v_OPAS_LEVEL = 2 AND v_ACTIVE_NODE = 'Y' -- Blackout BETWEEN '07:00:00' AND '21:00:00'
            THEN
            V_SENDALARM  := '/usr/local/bin/sendalarm.bsh -s "MINOR" -p "OEM_DB" -m "'||  V_TYPE || '" -N "'|| V_NODE || '"' ;
            INSERT INTO sysman.SEND_ALARM_LOG(target_name,metrics_entry,entry_date,entry_text)  
               VALUES (V_NODE,V_STATUS,SYSDATE, V_SENDALARM);
            sysman.shell(V_SENDALARM); 
            INSERT INTO SYSMAN.SENDALARM_DEBUG 
               VALUES(SYSDATE,V_SENDALARM,'V_SENDALARM');
           END IF;
    END IF;
EXCEPTION
       WHEN NO_DATA_FOUND THEN
              DBMS_OUTPUT.PUT_LINE('no_data_found');
       WHEN CASE_NOT_FOUND then
         DBMS_OUTPUT.PUT_LINE('case not found'); 
       WHEN OTHERS THEN
             DBMS_OUTPUT.PUT_LINE('OTHER ERRORS');
END;
/

WHEN OTHERS THEN
             DBMS_OUTPUT.PUT_LINE('OTHER ERRORS');