How to change Archive log Mode

SQL> startup mount;
ORACLE instance started.

Total System Global Area 612368384 bytes
Fixed Size 1250428 bytes
Variable Size 226495364 bytes
Database Buffers 377487360 bytes
Redo Buffers 7135232 bytes
Database mounted.
SQL> alter database noarchivelog;

Database altered.

SQL> alter database open;

Database altered.

SQL> select log_mode from v$database;

LOG_MODE
------------
NOARCHIVELOG