Dynamic Pages & Parameters - 404 Not Found Error

Question

I have the following dynamic page:
declare
M_subject varchar2(2000):= :message_subject;
begin
htp.print(''||M_subject||'');
htp.print('This is a Test - Passing a parameter to a Dynamic Page');
htp.p('Value: ' || M_subject);
end;
I also have another dynamic page that calls the above page and passes a parameter to it. And it works,..that is, the parameter gets passed to the page above, is assigned to M_subject and correctly prints on the screen.
The problem is that i want to do more then just simply print the variable, in particular, i'd like to use it in a sql query.
But when i add the following code into the above page
thebody varchar(2000);
select subject into thebody from MyTable where subject = M_subject;
htp.print(''||thebody||'');
it won't work. It compiles correctly but when i run the first dynamic page and call this 2nd page, i get a 404 Not Found error. Very strange because the page is definitely there.
So is there anything obvisous that i'm not doing correctly? Is my query not structured properly? Why can't i use this variable for something useful instead of just simply printing it on the screen?
Any comments, suggestions, fixes or ideas would be greatly appreciated.
thanks
chris

Answer 1

Put debug on on the application server for the dad you're using.
The error you are encountering will appear instead of the 404 not found error.
How:
in the home of your application server update the file
$ashome/Apache/modplsql:/conf/dads.conf
put ' PlsqlErrorStyle DebugStyle' in the dad you're using.
restart the application server, retry your dynamic page and the sql error will appear.