Re: About Hot backup.

From: Jared Still <jkstill_at_cybcon.com>
Date: Thu, 25 Mar 2004 07:12:26 -0800
Message-Id: <1080227545.11042.17936.camel@poirot>

As always, both.

Just more of it will be written in the redo log than normal if the tablespace is in backup mode.

IIRC the first time a block is written to when a tbs is in backup mode, the entire block is written to the redo log, which is not normally done.

This is so that recovery can take place in the case of a block split during backup of the datafile.

A block split can occur when the blocksize of the datafile and the blocksize of the database are different, and oracle is updating a block at the same time one or more (but not all) of the OS blocks that make up the database block is being written to the backup medium.

Following that initial full block write to redo, deltas of that block are written to the redo.

There is no doubt a lot more underlying detail, but that is the gist of it.

This is all moot if using RMAN though, as tablespaces are not put into backup mode in that case.

HTH Jared
On Thu, 2004-03-25 at 06:37, Senthil Kumar wrote:
> Hi,
>
> I have a doubt.
> When I'm taking the hot backup, where the new data will be written. In the
> datafile or in the redologs?.
>
> TIA
> Ram
>
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Received on Thu Mar 25 2004 - 09:09:46 CST