Enabling Archivelog Mode

Note: it is  recommended that performing a backup of the full database before  changing the archive status of a database.

• Check the database log mode 

[oracle@ora1 ~]$ sqlplus / as sysdba

SQL*Plus: Release 11.2.0.1.0 Production on Thu Apr 8 12:02:52 2010

Copyright (c) 1982, 2009, Oracle.  All rights reserved.

Connected to:

Oracle Database 11g Enterprise Edition Release 11.2.0.1.0 - Production

With the Partitioning, OLAP, Data Mining and Real Application Testing options

SQL> archive log list

Database log mode               No Archive Mode

Automatic archival             Disabled

Archive destination            USE_DB_RECOVERY_FILE_DEST

Oldest online log sequence          12

Current log sequence                       17

Or 

You can use v$database view to query archive log mode 


SQL> select log_mode from v$database;

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

If the database log mode is noarchivelog mode you can enable archivelog mode.

• Shutdown immediately  the database and get it backup in mount mode.

SQL> shutdown immediate

Database closed.

Database dismounted.

ORACLE instance shut down.

SQL> startup mount

ORACLE instance started.

Total System Global Area  849530880 bytes

Fixed Size                  1339824 bytes

Variable Size             511708752 bytes

Database Buffers          331350016 bytes

Redo Buffers                5132288 bytes

Database mounted.

SQL>

• Set archive log mode and open the database

SQL> alter database archivelog;

Database altered.

SQL> alter database open;

Database altered.

SQL> select log_mode from v$database;

LOG_MODE
------------
ARCHIVELOG

 Now we can  see that archive log mode is enabled.