On 12 Nov 2007 at 10:27, Jason Martin wrote: > On Mon, Nov 12, 2007 at 01:00:04PM -0500, Dan Langille wrote: > > On 12 Nov 2007 at 9:48, Jason Martin wrote: > > > > use, best practice is to dump the data to an ASCII file, then backup > > > > the file. > > > I'd suggest that it would be better to follow whatever procedure > > > is proscribed by the DBMS documentation :> This would be a very > > > poor way to back up Oracle, for example. > > > > Why is this a very poor way to back up Oracle? > > It is not really a backup of a database as far as Oracle is > concerned, it is a backup of an export. Oracle is all about > maintaining a coherent stream of 'redo' such that you can > effectively roll the database forward/back to any point in time. > The only recovery you can make from an export is to put the > database back as it was at the time of the export. A proper > backup allows you to recover the database up to the moment the > last 'commit' returned successfully against it, or any point > between the datafile backup and the most recent commit. Not > that export doesn't have its uses, but those uses are not for > backing up a production database.* > > Oracle will tell you the best way to back up Oracle is to use > RMAN and have your media manager (bacula in this case) back up > the resulting files from the flash recovery area. Another > option (the 'user-managed' option as they put it) is to put the > database in hot-backup mode and have bacula back up the 'live' > files. Putting Oracle in hot-backup mode puts additional > information in the redo logs such that it can recover from the > files having changed mid-backup. Hot-backups are an integral > feature to Oracle so there is no risk in doing it this way. That > said, always test your backups. > > RMAN is helpful since it makes sure you have all the necessary > files, while user-managed requires additional work to make sure > you have everything. > > http://6URL.com/1F5R (this is a q/a site from an Oracle VP) > > As far as bacula is concerned, you would likely have a > before-script that either invokes RMAN to generate a backupset, > or puts the db in hot-backup-mode, the job backs up the > appropriate files, and (if in hot-backup-mode) an after-job > command that turns off hot-backup-mode. These methods preserve > the database continuity, and combined with archive-logs allows > you to recover to the point-in-time immediately before a > failure. > > Other RDBMSs may have similiar setups. Exporting to a dump file > may be the correct procedure for MySQL, but I just wanted to > point out that special consideration needs to be taken for DBs > in general as they each have their own rules on the proper > backup methodology. Otherwise you are in for a rude surprise > when you go to restore. > > Now, if you were referring to RMAN-generated files as the 'ascii > files' mentioned above then we were talking about the same > thing, but I assumed you were referring to > exp/expdp/some-custom-tool generated files in this case as it is > a common misunderstanding. > > * Not that a paranoid DBA can't do it on an occasional basis, > but they should know the limitations of what they have and how > it is unlike a proper backup) >
John: that was well written. Thank you. Can we add the above, copy/paste, to http://wiki.bacula.org/ ? There is something similar for Oracle, but what you said explains more I think. See http://wiki.bacula.org/doku.php?id=application_specific_backups -- Dan Langille - http://www.langille.org/ Available for hire: http://www.freebsddiary.org/dan_langille.php ------------------------------------------------------------------------- This SF.net email is sponsored by: Splunk Inc. Still grepping through log files to find problems? Stop. Now Search log events and configuration files using AJAX and a browser. Download your FREE copy of Splunk now >> http://get.splunk.com/ _______________________________________________ Bacula-users mailing list Bacula-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/bacula-users
