The
main reason for running database in archive log mode is that one can provide 24 hour availability
and guarantee complete data recovery
It
is also necessary to enable ARCHIVELOG mode before one can start to use online database
backups.
To
enable ARCHIVELOG mode, simply change your database startup command script and
bounce the database
SQL>
shutdown immediate;
SQL>
startup mount exclusive;
SQL>
alter database archivelog;
SQL>
archive log start;
SQL>
alter database open;
NOTE1: Remember to take a
baseline database backup right after enabling archive log mode. Without it one
would not be able to recover. Also, implement an archive log backup to prevent
the archive log directory from filling – up.
NOTE2: ARCHIVE LOG mode was
introduced with Oracle Version 6 and is essential for database point – in – time
recovery. Archiving can be used in combination with online and offline database
backups.
NOTE3: You may want to set
the following INIT.ORA parameters when enabling ARCHIVELOG mode:
log_archive_start=TRUE,
log_archive_dest=... and
log_archive_format=...
NOTE4: You can change archive
log destination of a database online with ARCHIVE LOG START TO 'directory'
statement. This statement is often used to switch archiving between a set of
directories.
NOTE5: When running Oracle
Real Application Server (RAC), you need to shut down all nodes before changing
the database to Archive Log mode.