Help on Database Trigger

Question

Hi Users,
I have a requirement like whenever there is a insert or update on a table, some of the column values have to be inserted or updated into another table.
There is a table reporter_status with the following column. All are varchar2 data type
Source Table Name : reporter_status
Node             summary               mtr
1.1.1.1          Interface 9 xxx        66
1.2.3.4          Interface 10  xxx     03
10.10.1.2       Interface 11 xxx
2.2.2.2          Interface 5  xxx       90Target Table Name : interface_downtime
Node          Port           mtrDuring Insert:
If any new row is inserted into the above table and if the value of mtr is not null
1) extract only the numeric portion of the summary column i:e 9,10,11 and insert the above values into another table "interface_downtime" along with node
and mtr.
During Update :
When there is an update to mtr column the interface_downtime.mtr column should be summed based on the current node
I have written a trigger but it doesn't seem to work. I have no idea where I am wrong.
Your kind help is required.
My trigger Body:
CREATE OR REPLACE TRIGGER REPORTER.trigger_update_mtr
AFTER INSERT OR UPDATE
ON REPORTER.REPORTER_STATUS
REFERENCING NEW AS New OLD AS Old
FOR EACH ROW
WHEN (old.mtr is not null)
DECLARE
tmpPort  varchar2(3);
BEGIN
  IF INSERTING
  THEN
      tmpPort := substr(:old.summary,11,1);
      INSERT INTO interface_downtime values (:old.node,tmpPort,:old.mtr);
  END IF;    
  IF UPDATING
  THEN
            UPDATE interface_downtime
            SET       MTR   =  MTR + :OLD.MTR
            WHERE  NODE  = :old.node;
   END IF;
   EXCEPTION
     WHEN OTHERS THEN
       -- Consider logging the error and then re-raise
       RAISE;
END;
/

Answer 1

Change the trigger as below. The issue is that you are confused in old and new values. Its working fine as per my testing
CREATE OR REPLACE TRIGGER trigger_update_mtr
after INSERT OR UPDATE
ON REPORTER_STATUS
REFERENCING NEW AS New OLD AS Old
FOR EACH ROW
WHEN (new.mtr is not null)
DECLARe
tmpPort  varchar2(3);
BEGIN
    IF INSERTING
  THEN
        tmpPort := substr(:new.summary,11,1);
      INSERT INTO interface_downtime values (:new.node,tmpPort,:new.mtr);
  END IF;    
  IF UPDATING
  THEN
              UPDATE interface_downtime
            SET       MTR   =  MTR + :new.MTR
            WHERE  NODE  = :old.node;
   END IF;
   EXCEPTION
     WHEN OTHERS THEN
null;
END;