Any standard users are created with a password expiration date. By default it is 182 days. It is automatically renewed each time password is updated. When the dead line is reached the user is basically locked. Be aware a new password will not help if a user is being locked. Unlock the user first.
Anyway, if it is acceptable for a personal user account to be locked, it is on the contrary not acceptable for technical users. They have to be accessed and opened at all time.
For example a backup user has to be able to perform backup every day.
A failed backup could become a serious issue if a data recovery is necessary. In order to maintain this requirement the password expiration date has to be turned off.
Note: Turning off password lifetime is only disabling the password default expiration date, a valid password is still required in order to connect. Keep in mind, too many failed login will stop any future connection. In that case, you will have to reset failed connection attempts in order to allow new connections.
-- From an SQL console
-- To create a new administrtor user
CREATE USER USR_ADMIN_SYS PASSWORD FixSecret01 NO FORCE_FIRST_PASSWORD_CHANGE DISABLE PASSWORD LIFETIME;
-- To de-activate password expiration date of an existing user
CREATE USER MYBATCH_USER PASSWORD FixSecret01 NO FORCE_FIRST_PASSWORD_CHANGE;
ALTER USER MYBATCH_USER DISABLE PASSWORD LIFETIME;
-- To activate password expiration date of an existing user
-- ( 182 by default, value could be different if parameter 'maximum_password_lifetime' value has been changed. Table:M_PASSWORD_POLICY )
ALTER USER MYBATCH_USER ENABLE PASSWORD LIFETIME;