We had some requirement to disable some good amount of users. So it will not be a wise idea to get into Oracle and end date each and every user. So next option is to update from backend. But our worry is whether should we just update end_date column for all users and forget. That raised a question about what if we have to enable them again, what will happend to WF table sync. Then we used FND_USER_PKG details provided in Metalink Note : 364898.1 and we use it in cursor and we go the desired result. Here is what we did :
declare cursor cur1 is
select user_name from apps.fnd_user where LOWER(user_name) IN ('username','username', .......);
for all_user in cur1 loop
Happy Troubleshooting !!!
Note: Many Thanks to "hsawwan" for this.