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Home -> Community -> Mailing Lists -> Oracle-L -> RE: Tablespace Backup question
I need to bring in the backup class notes from the internals classes.
Colin is right.... and Oracle keeps both a header and footer section where the information is used to reconcile which blocks need "recovery"
this is from memory, I'd have to look up my notes to be certain
Rachel
>From: sean.hull_at_pobox.com
>Reply-To: ORACLE-L_at_fatcity.com
>To: Multiple recipients of list ORACLE-L <ORACLE-L_at_fatcity.com>
>Subject: RE: Tablespace Backup question
>Date: Mon, 05 Jun 2000 23:15:35 -0800
>
>
>On Mon, 5 Jun 2000 Colin.Shaw_at_phs.com wrote:
>
> > Actually, no. Oracle continues to write to the file *exactly* the same
>when
> > in hot-backup mode, with the exception of the checkpoint SCN. Also,
>full
> > blocks (not change vectors) are written to the redo log. You can find
>more
> > details about this at various web sites or in Velpuri's Backup Handbook.
> > Not sure if it's discussed in the Oracle Docs.
>
>I believe what you're saying, though I would like to at least confirm
>this. It seems *QUITE* weird to me. What if half a block (say 16k
>blocksize) had been written, and the OS context switches and then the
>other process starts reading the file. I mean how does Oracle avoid
>datafile corruption?
>
>Perhaps based on the SCN, Oracle knows that it needs to cleanup those
>datafiles for all transactions after a certain point, so doesn't worry
>about it. When you startup the db from the hotbackup, the files *ARE*
>corrupted then, but Oracle knows from the SCN where to recover from, and
>starts reading the redologs and writing those changes to the right places
>in the datafiles. I guess that might make some sense.
>
>I need to do some reading.
>
>Sean
>
>--
>Author:
> INET: sean.hull_at_pobox.com
>
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