RE: RMAN Disk Based Backup

Jared,  

Not sure if this was addressed, so here goes.... By default, *all* the files related to backup (includes archivelogs, backupsets, datafile copies) *as well* as Oracle-managed files, multiplexed copies of the online redo logs and control files, and most importantly, flashback logs (which can really grow!). However, only the total size of this area can be defined, and when there is disk pressure on account of rapid generation of archivelogs (or flasback logs) and adequate disk is not available, RMAN backups will fail with messages such as ORA-19809: limit exceeded for recovery files and ORA-19804: cannot reclaim 52428800 bytes disk space from 2147483648 limit. Be sure to calculate and set an adequate value for the DB_RECOVERY_FILE_DEST_SIZE parameter (thankfully, this can be changed online). Note that the space available for RMAN backup (via the DEST_SIZE parameter) is independent of the actual disk space available in that filesystem or ASM disk group; this value is simply a logical upper limit and exists to prevent some runaway job from filling up the disk space. The default value of 2GB is also *small* for a decent database... As with any other backup medium, you will have to define retention periods for backups, and RMAN will automatically manage the expiration of backups and files. This is another advantage of using the flash recovery area for backups. The various types of content (backupsets, archivelogs, datafile copies, flashback logs, etc.) are located within appropriately named subdirectories in the flash recovery area so managing this is easy, as you may choose to mount/manage them as separate filesystems. You can also become innovative in the location the flash recovery area - place it on an ASM for mirroring/protection/whatever or even a low cost SATA array if you are bothered about $$....

As for using it in Production: We haven't used it yet and are still trying it out as part of a 'get-at-least-the-RMAN catalog to 10g' project ;-)

Regards,
John Kanagaraj <><
DB Soft Inc
Phone: 408-970-7002 (W)  

Listen to great, commercial-free christian music 24x7x365 at http://www.klove.com  

• The opinions and facts contained in this message are entirely mine and do not reflect those of my employer or customers **

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From: oracle-l-bounce_at_freelists.org [mailto:oracle-l-bounce_at_freelists.org] On Behalf Of Jared Still
Sent: Sunday, August 21, 2005 1:48 AM
To: Oracle-L Freelists
Subject: RMAN Disk Based Backup

Perusing the Oracle 10g new features I see that Oracle has eliminated my objection to staging backups on disk.

Flash Backup and Recovery

This release supports automated, disk-based backup and recovery. The benefits include simplified and unified storage location for backups, archive logs, and any other files needed for Oracle recovery; automatic deletion of the files after they have been successfully backed up by the Recovery Manager (RMAN); the equivalent of a disk cache for tape, which reduces the time needed to restore a file from tape; and reduced risk of an out-of-space condition on disk, by deleting files that are no longer required for database recovery.

RMAN previously had no method to automatically retrieve files from a backup system that had been moved to tape after the initial backup to disk.

Has anyone here set this up and used it?

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Jared Still
Certifiable Oracle DBA and Part Time Perl Evangelist

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http://www.freelists.org/webpage/oracle-l Received on Tue Aug 23 2005 - 16:55:43 CDT