-- ************************************************************
-- *** Feel free to use this SQL-code, but please           ***
-- *** do not remove these copyright lines.                 ***
-- *** (C) Roger Felix - Lund - Sweden                      ***
-- *** [roger_felix@hotmail.com, web_master@work.utfors.se] ***
-- *** URL: http://hem.fyristorg.com/publish/index.html     ***
-- ************************************************************
-- **
-- ** REQUIRED GRANTS:
-- ** ~~~~~~~~~~~~~~~
-- ** grant select on SYS.V_$SESSION TO ?YOUR_USER?; 
-- ** grant select on SYS.V$SESSION  TO ?YOUR_USER?; 
-- **
-- ** DESCRIPTION:
-- ** ~~~~~~~~~~~~
-- ** THIS WILL CREATE A TRIGGER ON THE PROMPTED TABLE 
-- ** THAT PREVENTS UPDATES FROM OTHER SESSIONS.
-- **



set verify off
SET FEEDBACK OFF
SET HEADING OFF
PROMPT ...Checking grants...
select 'YOU MUST HAVE GRANTS ON V_$SESSION' from dual where
    0 = (select count(*) from USER_TAB_GRANTS_RECD 
            where TABLE_NAME = 'V_$SESSION' and SELECT_PRIV = 'Y');

COLUMN U NEW_VALUE UN
SELECT '&TABLE' U FROM DUAL;

DEFINE table_name = &UN

define csess = '-1'
column sid new_value csess noprint
select sid from v$session
 where audsid = userenv('sessionid');

CREATE OR REPLACE TRIGGER PREVENT_SESSIONS 
  BEFORE 
     INSERT OR UPDATE OR DELETE
         ON &table_name
REFERENCING OLD AS OLD NEW AS NEW FOR EACH ROW 

DECLARE
  the_sid   number;
BEGIN
 select sid INTO THE_SID from v$session
 where audsid = userenv('sessionid');

 -- ***********************************
 -- *** ADAPT FOR SESSION HERE: (!) ***
 -- ***********************************
 if THE_SID != &csess then
    raise program_error;
 end if;
END;
/

select 'DON''T FORGET TO DROP TRIGGER PREVENT_SESSIONS' FROM DUAL; 
set verify on;