Oracle Apps 11i/R12 Maintenance mode

Maintenance mode – (adadmin)
when you are going to install a patch on application the recommended option is that enable maintenance node. to bring the application in maintenance mode. when you enable or disable ‘maintenance mode’, adadmin will execute the script.
enable maintenance mode:
@>/ad_top/patch/115/sql/adsetmmd.sql enable
disable maintenance mode:
@>/ad_top/patch/115/sql/adsetmmd.sql disable
to verify if the environment is in maintenance mode or not execute following script.
select fnd_profile.value('APPS_MAINTENANCE_MODE') as status
from dual;
if the status
“maint” =       maintenance mode has been enabled and the users will not be able to login.
“normal”       =       maintenance mode has been de-activated and the users will be able to login.
how to enable the maintenance mode
set the environment variable on application instance.
run the ad administration utility by typing adadmin on console window. chose option 5 from the selection menu.
1.generate applications file menu.
2.maintain applications file menu.
3.compile/reload applications database entities menu.
4.maintain applications database entities menu.
5.change maintenance mode.
6.exit ad administration.