By default  the database log mode set to NOARCHIVELOG if you have installed oracle through the Typical installation. We can also change to Archive mode log.

The ARCHIVELOG This protects the database from both instance and disk failure.

How to change ARCHIVELOG:

Start SQL*Plus on your Terminal tool and execuate below command to login,
 

# sqlplus sys/password as sysdba


SQL*Plus: Release 11.2.0.2.0 Production on Wed Mar 18 18:03:07 2015



Copyright (c) 1982, 2011, Oracle.  All rights reserved.



Connected to:

Oracle Database 11g Express Edition Release 11.2.0.2.0 - 64bit Production

SQL> 

To check your database log mode using below command,


SQL> ARCHIVE LOG LIST



Database log mode             No Archive Mode

Automatic archival            Disabled

Archive destination           USE_DB_RECOVERY_FILE_DEST

Oldest online log sequence     1

Current log sequence           2

If the database is open, shut it down,



SQL> SHUTDOWN



Database closed.

Database dismounted.

ORACLE instance shut down.

Now, Mount the database:


SQL> STARTUP MOUNT



ORA-00845: MEMORY_TARGET not supported on this system

If you may get an above error need to increase tempfs spcace, just refer on next post,


SQL> STARTUP MOUNT



ORACLE instance started.



Total System Global Area  814227456 bytes

Fixed Size            2230896 bytes

Variable Size          541066640 bytes

Database Buffers      268435456 bytes

Redo Buffers            2494464 bytes

Database mounted.

Execute command to set database log move is "Archive Mode"


SQL> ALTER DATABASE ARCHIVELOG;



Database altered.

Now check the configure,


SQL> ARCHIVE LOG LIST



Database log mode           Archive Mode

Automatic archival           Enabled

Archive destination           USE_DB_RECOVERY_FILE_DEST

Oldest online log sequence     1

Next log sequence to archive   2

Current log sequence           2