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Database ARCHIVELOG mode: Overview

An Oracle database could be in ARCHIVELOG or NON ARCHIVELOG mode. When the database is in ARCHIVELOG mode one or more ARC process(es)  are taking backups of the redo log files when the redo logs are full or switched. That assure that all the database operations are kept in 2 places (in data files and in archive log files). Having the database in ARCHIVELOG mode assure us that the data will not be lost even if the original data (from datafiles) will become inaccessible or will be deleted accidentally. 

Is my database in ARCHIVELOG mode ?

To see if the database is in archivelog mode the following command could be used:

select NAME, LOG_MODE, ARCHIVELOG_CHANGE# from v$database;

How could I enable the ARCHIVELOG mode ?

1)  assure that we have the following parameters in init.ora:

      log_archive_dest_1='location=C:\OHome_9i\ARC'
      log_archive_start=TRUE                  -->obsolete for 10g and higher.

2)  startup mount

3)  alter database archivelog;  (enable automatic archiving)

     alter database archivelog MANUAL;   (ALTER SYSTEM ARCHIVE LOG ALL; must be run to archive the log files) 

How could I disable the ARCHIVELOG mode ?

1)  startup mount

2)  alter database noarchivelog; 

More information about  this subject ( Database ARCHIVELOG mode ) you can get from  www.in-oracle.com