How to expire user passwords using SQL commands?

Run the SQL statement  below to expire an account:

SQL>  ALTER USER <username>  PASSWORD EXPIRE;

Example:

SQL> conn sys/orcl@to_primary as sysdba
Connected.
SQL> alter user mereba password expire;
 User altered.
 SQL>

Expiring an account’s password means when user tries to login he/she will be forced to change the password.

Now, lets try to login through the expired account above:

SQL> conn mereba/mereba@to_primary
ERROR:
ORA-28001: the password has expired
  Changing password for mereba
New password:
Retype new password:
Password changed
Connected.
SQL>

Note: when we create a database there many users created by default. It is recommended to lock the accounts and expire their passwords if we are not currently using them.