Two users are required to manage the password of another user.
Example
         Assuming login policy 
Sales1 has the
            
CHANGE_PASSWORD_DUAL_CONTROL option enabled, 
User3
         is assigned 
Sales1, and 
User1 and 
User2
         have been granted the necessary privileges to change the password of
         
User3, these statements set the two password parts for
            
User3 to 
NewPassPart1 and 
NewPassPart2:
User1 types:
            
ALTER USER user3 IDENTIFIED FIRST BY NewPassPart1
 
User2
            types:
ALTER USER user3 IDENTIFIED LAST BY NewPassPart2