Handling Oracle error messages

Question

I'm hoping this is a simple question.
I have an updatable report I'm using to collect data. It's pretty vanilla - I just used the default templates. I have a unique index constraint on the form's underlying table. When I violate the constraint and attempt to save a row, I get redirected to what looks to be a default error page that isn't very user friendly.
Can someone tell me how I can specify a different error message depending on the error number Oracle returns?
Thanks for any info.

Answer 1

The whole problem is divided in two parts: Exception is defined or not, I'll show you haow to handle exception that do not exist and want to trap them.
I saw that there is no named exception for ORA error "-00054", which is raised when record is locked. So I define my exception as:
busy_resource EXCEPTION;
  PRAGMA EXCEPTION_INIT(busy_resource, -00054);Now to handle this exception in the Appex process looks like:
begin
  ...your code ...
  :PXX_msg := 'OK!';
exception
  when busy_resource THEN
    :PXX_msg := 'Record is locked. Try later';
  when others then
    :PXX_msg := 'Unknown error!;
end;where "PXX_msg" is hidden item acesable on the page, XX represent page number.
And in "Process Error Message" part of process don't put anything because all errors are handled and error will never happened. If you want that part put in excepttion part "RAISE;" command so erro will be raised!!!
And in "Process Success Message" of the same process put also:
"&PXX_msg."
So you can see the result in much pleasent way!
You have the same variable as result and now all to do is imagine exceptions that could happened. For the first time allways try to put some logging in "WHEN OTHERS THEN" part top collect as much as possible errors that could happened.
Hope this helps!