While the database is OPEN, we can close the database to the MOUNT status, and we can enable or disable the archivelog and we can dismount the database
SQL> select status from v$instance;
STATUS
------------
OPEN
SQL>
SQL> alter database close;
Database altered.
SQL>
SQL>
SQL> select status from v$instance;
STATUS
------------
MOUNTED
SQL> alter database noarchivelog;
Database altered.
SQL> alter database archivelog;
Database altered.
SQL>
SQL> alter database dismount;
Database altered.
SQL>
SQL> select status from v$instance;
STATUS
------------
STARTED
SQL>
SQL> startup force;
ORACLE instance started.
Total System Global Area 1677718256 bytes
Fixed Size 8897264 bytes
Variable Size 771751936 bytes
Database Buffers 889192448 bytes
Redo Buffers 7876608 bytes
Database mounted.
Database opened.
SQL>