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Re: Database backup question.

From: Tim Gorman <>
Date: Thu, 23 May 2002 19:13:25 -0800
Message-ID: <>


Theoretically, the online redo log files are be necessary, but the world has a habit of making a shambles of the theoretical. Let's say, in the event that you automate your Friday script, you'll probably come to realize that SHUTDOWN IMMEDIATE is far from perfect (as well as far from immediate!). Over time, you'll probably construct some kind of "fail-safe" mechanism to SHUTDOWN ABORT if the initial SHUTDOWN IMMEDIATE doesn't shut down after a period of time. Pretty standard thing that DBAs have been writing for years. Hopefully, after the SHUTDOWN ABORT they also STARTUP RESTRICT and then SHUTDOWN NORMAL, but you can't count on it...

So, here's the point: what if you take a cold backup in NOARCHIVELOG mode after a SHUTDOWN ABORT (that should have been a SHUTDOWN IMMEDIATE and wasn't) and you have *not* backed up those online redo log files? Answer: unusable backup. So, back up everything: all datafiles, controlfiles, and online redo logfiles. The latter are not too big anyway -- what's the point of excluding them?

It is wise to take a cold backup after a clean shutdown, but you can even get a valid backup after a SHUTDOWN ABORT or a crash if you've backed up the online redo archive log files. When you restart Oracle, an instance recovery will occur automatically, and you might not even know it. Just be certain that the instance is truly "dead" when you take your "cold" backup...

With regards to switching between ARCHIVELOG and NOARCHIVELOG, it's a waste of effort from a recoverability standpoint. At most it may be interesting, but as soon as you switch out of ARCHIVELOG mode, nothing you've done while in ARCHIVELOG mode is valid anymore. Leave it one way or the other, and then leave it...

...just my $0.02...

Another $0.02: use RMAN for your cold backups. Then you won't forget anything, because RMAN will remember for you...

Hope this helps...


  Hi All,

  I need to perform a consistent backup for my whole database every Friday by using operating system utilities. My database has been currently operating in NOARCHIVELOG mode, so the only files need to be backed up are datafiles, control files, the initialization parameter file and other oracle product initialization files (Based on Oracle8.1.6 Backup and Recovery Guide). Since the files in this type of backup are all consistent and do not need recovery, so the online logs are not needed. Since online redo logs is very crucial for recovery, so my question is do I need to back up the online redo log files as I choose to perform cold backup type for my entire database weekly? Here is step by step what I did to back up the whole database:

  after the database was closed cleanly and all the above mentioned files had been backed up into the tape. I had to restart the database and mount but not open, then switched between NOARCHIVELOG mode to ARCHIVELOG mode in order to archive the online redo log files. Finally, I copied all archived redo log files into the tape while the database was open and operated in ARCHIVELOG mode. when it was all done, I then switched the database back to NOARCHIVELOG mode. Just wondered whether my procedure to perform a whole consistent database backup is correct? Am I safe to this point? Your help is greatly appreciated it. Your help is greatly appreciated.

  Thanks in advance,


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Author: Tim Gorman

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