Switches to another user.
set proxy user_name switches to a new user with all the permissions of the new user and none of the permissions of the original user.
The new user can always switch back to the original user, whether or not the new user has “sa” permission, by entering set proxy without a user name.
set proxy user_name verify password passwd allows a user without sa permission to switch to another user—if the correct password for user_name is entered.
set proxy user_name requires “sa” permission. Any user can execute set proxy and set proxy user_name verify password passwd.