How to Log Alter Column DDL Operations - oracle

Question

I need to create a database trigger which will record each alter (Add Column,Modify Column,Drop Column) statements in a specific table using Oracle's schema trigger. How to get it ?
I tried the code below so far :
TRIGGER after_ddl_creation
after CREATE ON SCHEMA
DECLARE
V CLOB;
BEGIN
FOR REC IN(SELECT TEXT FROM user_source WHERE NAME=SYS.DICTIONARY_OBJ_NAME)
LOOP
V:=V||REC.TEXT;
END LOOP ;
INSERT INTO myAudit VALUES
(SYS.DICTIONARY_OBJ_NAME,SYS.DICTIONARY_OBJ_TYPE,SYSDATE,USER,NULL,NULL,V);
END;

Answer 1

You can use such a database trigger :
create or replace trigger after_ddl_creation after ddl on schema
declare
v_oty varchar2(75) := ora_dict_obj_type;
v_don varchar2(75) := ora_dict_obj_name;
v_evt varchar2(75) := ora_sysevent;
v_olu varchar2(75) := nvl(ora_login_user,'Undefined Schema');
v_sql ora_name_list_t;
v_stm clob;
v_sct owa.vc_arr;
n pls_integer;
n_max pls_integer := 10000;
--> can log upto ten-thousand rows of "text" value, within "stmt" column,
--> which can be accessed by using (`[user|all|dba]_source`) views.
begin
v_sct(1) := 'SESSIONID';
v_sct(2) := 'IP_ADDRESS';
v_sct(3) := 'TERMINAL';
v_sct(4) := 'OS_USER';
v_sct(5) := 'AUTHENTICATION_TYPE';
v_sct(6) := 'CLIENT_INFO';
v_sct(7) := 'MODULE';
for i in 1..7
loop
v_sct(i) := sys_context('USERENV',v_sct(i));
end loop;
select decode(v_sct(1),0,null,v_sct(1)),
decode(upper(v_sct(3)),'UNKNOWN',null,v_sct(3))
into v_sct(1),v_sct(3) from dual;
n := ora_sql_txt( v_sql );
if n > n_max then
n := n_max;
end if;
for i in 1..n
loop
v_stm := v_stm || v_sql(i);
end loop;
if ( evt = 'ALTER' and oty = 'TABLE'
and regexp_like(v_stm,'Add|Modify|Drop','i') ) then
insert into myAudit(ts,usr,evnt,stmt,sessionid,ip,terminal,os_user,auth_type,
object_type,object_name,client_info,module_info)
values(sysdate,v_olu,v_evt,v_stm,v_sct(1),v_sct(2),v_sct(3),v_sct(4),v_sct(5),
v_oty,v_don,v_sct(6),v_sct(7));
end if;
end;
by recreating myAudit table due to the above INSERT statement.