Muttating in triggers

Question

Hi!
When i move code into database from aplication i have problem with database control of muttating data.
I have to call plsql procedure wich do some actions by example after updating some data.
Example:
create table tab (col1 Number, col2 ..., colN Number) ;
CREATE OR REPLACE TRIGGER tr_tab_upd AFTER UPDATE OF col2,col3
ON tab
REFERENCING OLD AS OLD NEW AS NEW
FOR EACH ROW
BEGIN
DECLARE
p_res ....
BEGIN
proc(:NEW.COL1,p_res);
If (p_res....) Then
Raise ERROR;
End If;
END;
end;
Where proc is plsql procedure and inside this procedure i ONLY READ data from tab (vs. calling procedure with many arguments - :NEW.COL1, :NEW.COL2, ... , :NEW.COLN - asume that number of columns is big and that procedure will be called not only from trigger). Is there possible to tell database before calling (something like commit :)) that i will only select data without changing in table tab, but leave possibility to break transaction which fire trigger depending on result of procedure?

Answer 1

Thanks, there is many solutions but i try to find best and my idea is not duplicate objects (creating new log tables) because i have many tables that i have to resolve.
Simply i have to find best way to move most code from aplications to database. One of my solutiuon is to make procedure like this:
create or replace procedure proc (ar_pk In number, ar_res Out Varchar2,
ar_col1 In N/V Default null, ar_col2 In N/V Default null,..., ar_colN In N/V Default null) is
v_col1 N/V;
v_col2 N/V;
v_col3 N/V;
BEGIN
If (ar_col1 Is Not null) Then -- procedure is called from trigger
v_col1:=ar_col1;
v_colN:=ar_colN;
Else
BEGIN
Select col1,...,colN
Into v_col1,...,v_colN
From tab
Where col1=ar_pk; -- Asume that col1 is primary key
EXCEPTION
END;
End if;
END;
When call proc from trigger send alll arguments as :NEW.COL1,..., :NEW.COLN. Otherway just call proc (pk,res)
There are no new tables. Be aware that in future table tab will be altered in this case you must change trigger and procedure, may be not other
code who call proc and not log table.
Have anyone better idea - this is big job and will like to know easy way.