SQL & PL/SQL

Hi Guys,

I have to do db refresh from the build .For this I have to kill the sessions and drop the users and recreate the users with the latest build.As the application is running and there are some idle sessions, I have to kill the sessions and drop the users for that I am using a code as below

DECLARE
v_alt_stmt VARCHAR2(1000) := 'ALTER SYSTEM KILL SESSION ''';
v_kill_stmt VARCHAR2(1000);
CURSOR cur_session IS
SELECT s.type type,
s.sid sid,
s.serial# srl_no,
s.username user_name,
s.PROGRAM prog_name
FROM v$session s JOIN gv$process p ON p.addr = s.paddr and s.type='USER';

BEGIN
EXECUTE IMMEDIATE 'ALTER SYSTEM ENABLE RESTRICTED SESSION';
DBMS_OUTPUT.PUT_LINE('The Session has been put in the restricted mode');
FOR v_cur_ssn IN cur_session
LOOP
BEGIN
v_kill_stmt := v_alt_stmt || v_cur_ssn.sid || ',' || v_cur_ssn.srl_no || '''';
DBMS_OUTPUT.PUT_LINE(v_kill_stmt);
EXECUTE IMMEDIATE v_kill_stmt;

EXCEPTION
WHEN others THEN
-- DBMS_OUTPUT.PUT_LINE('The current sessions sid is ' || v_cur_ssn.sid || ' and the srl no is ' || v_cur_ssn.srl_no || ' can not be killed');
END;
END LOOP;
EXECUTE IMMEDIATE 'ALTER SYSTEM DISABLE RESTRICTED SESSION';
DBMS_OUTPUT.PUT_LINE('The restricted mode of the system has been removed');
END;

But sometimes after killing the sessions there are some os processes are going on,to avoid that I have to use 'ALTER SYSTEM DISCONNECT SESSION ''' and 'MMEDIATE' it is workig fine .

Can Any one tell me the logical difference between kill sessions and disconnect


Any information will be highly appreciated.

Thanks in advance

Prafulla