Re: Oracle Database Pool Block Flushing

From: Sybrand Bakker <postmaster_at_sybrandb.demon.nl>
Date: Mon, 27 Sep 1999 22:28:33 +0200
Message-ID: <938464196.15615.0.pluto.d4ee154e@news.demon.nl>

Oracle always write to the redolog files first. Also it maintains a system commit number (SCN) in the control file header, the redo log file header
and the database file header (if appropiate). If the transaction commits the SCN will be written out to all files.
If the transaction didn't commit before the database crashed, whether DBWR did already write to the datafiles or not, the transaction will be rolled back (the so-called before image info also being written to the redolog file).

Hth,

--
Sybrand Bakker, Oracle DBA
<corcorank_at_my-deja.com> wrote in message news:7snko0$55g$1_at_nnrp1.deja.com...
> My qustion is this. As I understand it the redo
> log buffers are flushed when they fill or when a
> commit is issued. If the machine fails and
> restarts how does Oracle ensure that DBWR hasn't
> written changed datafile blocks to their
> respective datafiles? Does DBWR somehow ignore
> updated blocks that haven't had their log updates
> externalised or is there some other process at
> work?
>
>
>
> Sent via Deja.com http://www.deja.com/
> Before you buy.
Received on Mon Sep 27 1999 - 15:28:33 CDT