Achive Logs

Archive log mode is necessary for hot backups and point-in-time recovery.
By default the database is created in noarchivelog mode.
Setting Archive log format and Destinations:
The following parameters need to be set in order to use archivelog mode:
log_archive_start = TRUE
log_archive_dest_1 = 'LOCATION=/d01/archive'
log_archive_dest_state_1 = ENABLE
log_archive_format = %d_%t_%s.arch

Archive log modes:
Enable and disable archive log modes in oracle database,An Oracle database can run in one of two modes.
archive log mode and noarchive log mode By default, the database is created in NOARCHIVELOG mode.
This command will check to see if you have altered your database to run in ARCHIVELOG mode.
Enable Archivelog Mode 
SQL>shutdown immediate
SQL>startup mount
SQL>alter database archivelog
SQL>alter database open;
To Disable Archivelog mode
SQL>Shutdown immediate
SQL>startup mount
SQL>alter database noarchivelog
SQL>alter database open;
SQL>archive log list
Check the archive log mode
SQL>select log_mode from v$database