Can I change the profile of oracle sys user?
Our monitoring keeps telling us the password of sys has expired. The &quot;Default“ profile has a standard limit of 180 days.

You should not try to change the Profile for internal, Oracle accounts (indeed, there is one, very oddly named, account that you cannot changed in any way, shape or form!).
You should not change the behaviour of the DEFAULT profile.
The &quot;default&quot; behaviours can change from version to version of Oracle Database and so may be unexpectedly &quot;reset&quot; on you, during an upgrade.
If you want to tie down these behaviours, define your own Profiles and configure them as you need them.
CREATE PROFILE APPLICATION_ACCOUNTS 
    LIMIT 
    PASSWORD_LIFETIME UNLIMITED 
    ; 
ALTER USER APP_1_ACCOUNT PROFILE APPLICATION_ACCOUNTS ; 
ALTER USER APP_2_ACCOUNT PROFILE APPLICATION_ACCOUNTS ; 

CREATE PROFILE INTERACTIVE_USER 
    LIMIT 
    PASSWORD_LIFETIME 180 
    . . . 
    ; 
ALTER USER FRED   PROFILE INTERACTIVE_USER ; 
ALTER USER BARNEY PROFILE INTERACTIVE_USER ; 

Anything you don't specify in your custom profiles will, of course, be &quot;inherited&quot; from the DEFAULT one.