Why and How to enable archive log mode in Oracle

 Why ?

You will need to enable archivelog mode if you need any one of the below ::

• To restore your DB to last change occur in case of failure in the case of an operating system or disk failure.

• To take online backup -hot backup- backup while database is open.

• To use Data guard feature (standby DB) you need to enable this as well.

How ?

Before you enable archive log mode , you can check the current situation mode and set the location the archive log:

1. To check current archive log status

archive log list;

       2.To set archive log location

alter system set log_archive_dest_1='LOCATION=/disk/archive' scope=spfile ;

The following steps switch the database archiving mode from NOARCHIVELOG to ARCHIVELOG:

1. Shut down the database instance.

   SHUTDOWN immediate ;

2. Start a new instance and mount, but do not open, the database.

   STARTUP MOUNT;
   

   To enable or disable archiving, the database must be mounted but not open.

3. Change the database archiving mode. Then open the database for normal operations.

   ALTER DATABASE ARCHIVELOG;
   ALTER DATABASE OPEN;

** In case you need to stop archive log mode, in mount state you may use the below :

ALTER DATABASE NOARCHIVELOG;