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RMAN - Backing Up Archived Logs

By: hitechwriter

Backing Up Archived Redo Log Files with BACKUP ARCHIVELOG

To back up archived redo logs, use the BACKUP ARCHIVELOG command at the RMAN prompt. This example uses a configured disk or sbt channel to back up one copy of each log sequence number for all archived redo logs:
BACKUP ARCHIVELOG ALL;

Even if your redo logs are being archived to multiple destinations and you use RMAN to back up archived redo logs, RMAN selects only one copy of the archived redo log file to include in the backup set. (Since logs with the same log sequence number are identical, there is no need to include more than one copy.)

You can also specify a range of archived redo logs by time, SCN, or log sequence number, as in the following example:
BACKUP ARCHIVELOG
FROM TIME 'SYSDATE-30' UNTIL TIME 'SYSDATE-7';

Automatic Online Redo Log Switches During Backups of Archived Logs

When taking a backup of archived redo logs that includes the most recent log (that is, a BACKUP ... ARCHIVELOG command is run without the UNTIL or SEQUENCE option) if the database is open, then before beginning the backup, RMAN will switch out of the current online redo log group, and all online redo logs that have not yet been archived, up to and including the redo log group that was current when the command was issued. This ensures that the backup contains all redo that was generated prior to the start of the command.

Using BACKUP ARCHIVELOG with DELETE INPUT or DELETE ALL INPUT

You can specify the DELETE INPUT or DELETE ALL INPUT clauses for the BACKUP ARCHIVELOG command to delete archived logs after they are backed up, eliminating the separate step of manually deleting the archived redo logs. With DELETE INPUT, RMAN only deletes the specific copy of the archived redo log chosen for the backup set. With DELETE ALL INPUT, RMAN will delete each backed-up archived redo log file from all log archiving destinations.

For example, assume that you archive to /arc_dest1, /arc_dest2, and /arc_dest3, and you run the following command:
BACKUP DEVICE TYPE sbt
ARCHIVELOG ALL
DELETE ALL INPUT;

In this case RMAN backs up only one copy of each log sequence number in these directories, and then deletes all copies of any log that it backed up from the archiving destinations. If you had specified DELETE INPUT rather than DELETE ALL INPUT, then RMAN would only delete the specific archived redo log files that it backed up (for example, it would delete the archived redo log files in /arc_dest1 if those were the files used as the source of the backup, but it would leave the contents of the /arc_dest2 and /arc_dest3 intact) .
If you issue BACKUP ARCHIVELOG ALL or BACKUP ARCHIVELOG LIKE '...', and there are no archived redo log files to back up, then RMAN does not signal an error.

Backing Up Logs with BACKUP ... PLUS ARCHIVELOG

You can add archived redo logs to a backup of other files by using the BACKUP ... PLUS ARCHIVELOG clause. Adding BACKUP ... PLUS ARCHIVELOG causes RMAN to do the following:
Runs the ALTER SYSTEM ARCHIVE LOG CURRENT command.
Runs BACKUP ARCHIVELOG ALL. Note that if backup optimization is enabled, then RMAN skips logs that it has already backed up to the specified device.
Backs up the rest of the files specified in BACKUP command.
Runs the ALTER SYSTEM ARCHIVE LOG CURRENT command.
Backs up any remaining archived logs generated during the backup.
This guarantees that datafile backups taken during the command are recoverable to a consistent state.

To back up archived redo logs with BACKUP ... PLUS ARCHIVELOG:
After starting RMAN, run the BACKUP ... PLUS ARCHIVELOG command at the RMAN prompt . This example backs up the database and all archived logs:
BACKUP DEVICE TYPE sbt
DATABASE PLUS ARCHIVELOG;

For more details on RMAN Backing Up you can view on ***** DO NOT PLACE LIVE URL LINKS IN THE ARTICLE BODY***** href="http://oracleDbaSupport.co.uk">ORACLE DBA SUPPORT

Article Source: http://articleaddict.com

http:// OracleDbaSupport.co.uk is a blog site of Sagar Patil, an independent oracle consultant with a great understanding of how the Oracle database engine & Oracle Applications work together.

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