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Thursday, September 23, 2010

Enable Archive mode in oracle 10g



Noarchive Mode:


When you run your database in NOARCHIVELOG mode, you disable the archiving of the redo log. The database control file indicates that filled groups are not required to be archived. Therefore, when a filled group becomes inactive after a log switch, the group is available for reuse by LGWR.
NOARCHIVELOG mode protects a database from instance failure but not from media failure.
In NOARCHIVELOG mode you cannot perform online tablespace backups, nor can you use online tablespace backups 



Archive Mode:



When you run a database in ARCHIVELOG mode, you enable the archiving of the redo log. The database control file indicates that a group of filled redo log files cannot be reused by LGWR until the group is archived. A filled group becomes available for archiving immediately after a redo log switch occurs.
The archiving of filled groups has these advantages:
  • A database backup, together with online and archived redo log files, guarantees that you can recover all committed transactions in the event of an operating system or disk failure.
  • If you keep an archived log, you can use a backup taken while the database is open and in normal system use.


    Benifits:


1. We can able to take database backup ONLINE.
2. No Need to Down Oracle DB Server
3. We can better Manage our Backup Policy through RMAN
4. Limited DBA task
5. We can able to RECOVER our database point-in-time


to enable Archive mode:


1. shutdown immediate
2. startup mount 
3. alter database archivelog;
4. alter database open



optionaly you can set a destination for archiving else archive files will create in Flash_Recovery_Area




--for win   alter system set log_archive_dest_1='location=c:\youfolder';

--for linux alter system set log_archive_dest_1='location=/u01/app/archive';




you can set upto 10 destination (including flash recover area)

using parameter log_archive_dest_n       where n is from 1 to 10.




some views that can provide us with information reguarding archives, such as:



v$DATABASE
v$ARCHIVED_LOG
V$ARCHIVE_DEST
V$ARCHIVE_PROCESSES
v$BACKUP_REDOLOG
v$LOG
V$LOG_HISTORY




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