How to change oracle user password using SQL commands?

We can modify oracle user password either using ALTER USER command or SQL*PLUS  PASSWORD command.

Using alter user command:

SQL > alter user <user> identified by   <newpassword>

Example:

SQL> conn sys/orcl@to_primary as sysdba
Connected.
SQL> alter user mereba identified by mereba123;
 User altered.
SQL>

Using SQL*PLUS command:

SQL> passw <user>

Example:

SQL> conn sys/orcl@to_primary as sysdba
Connected.
SQL> passw mereba
Changing password for mereba
New password:
Retype new password:
SP2-0650: New passwords do not match
Password unchanged
SQL>