[sql] Oracle: how to set user password unexpire?

There is some construction

ALTER USER scott PASSWORD EXPIRE

But how can I similair set password to unexpired state?

If you create a user using a profile like this:

CREATE PROFILE my_profile LIMIT
       PASSWORD_LIFE_TIME 30;
ALTER USER scott PROFILE my_profile;

then you can change the password lifetime like this:

ALTER PROFILE my_profile LIMIT
  PASSWORD_LIFE_TIME UNLIMITED;

I hope that helps.

While applying the new profile to the user,you should also check for resource limits are "turned on" for the database as a whole i.e.RESOURCE_LIMIT = TRUE

Let check the parameter value.
If in Case it is :

SQL> show parameter resource_limit
NAME                                 TYPE        VALUE
------------------------------------ ----------- ---------
resource_limit                       boolean     FALSE
Its mean resource limit is off,we ist have to enable it. 

Use the ALTER SYSTEM statement to turn on resource limits. 

SQL> ALTER SYSTEM SET RESOURCE_LIMIT = TRUE;
System altered.

The following statement causes a user's password to expire:

ALTER USER user PASSWORD EXPIRE;

If you cause a database user's password to expire with PASSWORD EXPIRE, then the user (or the DBA) must change the password before attempting to log in to the database following the expiration. Tools such as SQL*Plus allow the user to change the password on the first attempted login following the expiration.

ALTER USER scott IDENTIFIED BY password;

Will set/reset the users password.

See the alter user doc for more info