DBWn writes only the committed records to the datafiles. The blocks having
committed records are known as dirty blocks/Buffers. When checkpoint occurs
or free buffer threshold reaches, DBWn writes theses dirty buffers to the
datafiles. Once the dirty blocks are written, they become free and available
for further use.

-----Original Message-----
From: Sudheendra Vijaykumar [mailto:sudhi76@...]
Sent: Tuesday, November 05, 2002 9:00 AM
To: OraTechSupportGroup@yahoogroups.com
Subject: Re: [OraTechSupportGroup] What happens during large insert
without commit


Hi Sameer,

DBWR will write both committed and uncommitted data to
the datafiles. When a commit is issued, then only the
buffers that were still lying around in the cache will
be cleaned out to reflect the commit. The other
buffers in the datafile will still have the entry
open. When somebody else visits that block, then that
person will do the clean out and this is referred to
as 'delayed block cleanout'.

Thanks,
Sudhi.
--- sameer wadhwa <samoracle@...> wrote:
> Hi all,
>
> One of our developer is inserting a 1Gb of datafile
> without commiting a DATA.
>
> As LGWR copies commited and uncommitted data from
> redo log buffer to redo log files.
>
> Will the DBWm writes only comitted data from the
> redo
> log files to datafile or it will write commited +
> uncommited data to the datafiles.
>
> In the our case if the 1GB of datafiles are
> inserting
> into the database without commit and REDO LOG file
> size is 20 MB, then after switch, once checkpoint
> raise DBWn writes uncommited data to datafiles.
> When
> user commit the data, how the datafile knows which
> records are comitted.
> If you says during checkpoint datafile writes only
> commited data, then in our case lots of redo log
> switches happens before user commits.How the records
> of commited data will be written now
>
> Let me clear the login
>
> Thanks
>
>
>
> =====
> Sameer Wadhwa
> 508-366-6182(H)
> s_wadhwa@...
>
> __________________________________________________
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> http://hotjobs.yahoo.com/
>

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