This article helps in changing the password for Oracle user using API FND_USER_PKG.CHANGEPASSWORD.
This API is tested in R12.1.3
v_user_name VARCHAR2 (100) := 'OPERATIONS';
v_new_password VARCHAR2 (100) := :NEWPASSWORD;
v_status BOOLEAN := NULL;
v_status := fnd_user_pkg.changepassword (v_user_name, v_new_password);
DBMS_OUTPUT.put_line ( 'Password is changed successfully for the user '|| v_user_name);
DBMS_OUTPUT.put_line('Error encountered while setting new password to the user and the error is '|| SQLERRM);