[ORACLE 9] Select For Update Nowait - Managing the Nowait

Question

Hi,
Our application ( Oracle E Business R11) has a Form that allows Updates.
The problem is, when a user updates a record in the form, we want to prevent another user to open the same form, to avoid locks.
So I thought that I could
a) issue a 'select ...for update nowait',
b) get a code from Oracle
c )and use this code to prevent the form to be reopened.
I tried catching the Nowait in the exception section but I cannot get it to work.
Here is my code:
declare
  v_var varchar2(40) := '---';
lv_nom           tmp_delegue_jbm.del_nom%type;
begin
v_var := 'Phase 1';
select   del_nom
into     lv_nom
from     tmp_delegue_jbm
where    del_id = 3
for update of del_nom nowait;
dbms_output.put_line( 'Phase:  ' || v_var  );
v_var := 'Phase 2';
update tmp_delegue_jbm
set del_nom = del_nom || ' in'
where del_id = 3;
dbms_output.put_line( 'Phase:  ' || v_var  );
exception
   when others then -- Should deal with the nowait situation
         dbms_output.put_line( 'Error:  ' || v_var || ' - ' || sqlerrm );
end;
[End Code]
Many thanks                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                       

Answer 1

Far easier to poke a value into memory using DBMS_APPLICATION_INFO.SET_ACTION or SET_MODULE and have any session calling the form check first to see of another session has it already opened. Just make sure your exception handlers clear the lock.
http://www.morganslibrary.org/reference/dbms_applic_info.html