Re: REDO LOG Concepts

Hi Peter,

I think Oracle does issue a checkpoint before shutdown immediate? Doesn't it? Otherwise how will all the file headers be in sync?

Please correct me if I am wrong.

Deepak

On 5/17/07, Peter McLarty <p.mclarty_at_cqu.edu.au> wrote:
>
> Hi Deepak
> You will likey find that your database when you succeed in opening it does
> not show the transaction as successful. This is because the commit caused
> the lgwr to write your activity to the redo logs however the dbw has not at
> this time written your transaction to the datafile. This means that when you
> issued the shutfown immediate, the redo log items are not necessarily
> written to the datafiles. There is no requirement for Oracle to do this, I
> suspect that they do.
>
> The concepts guide is not clear on this with an immediate shutdown,
> however if it was a shutdown abort your tranaction would in effect be rolled
> back(not a true roll back) as in the abort Oracle waits until the restart to
> apply or not apply information in the redo files.
>
>
>
> ------------------------------
> *From:* DBA Deepak [mailto:oracle.tutorials_at_gmail.com]
> *Sent:* Thursday, 17 May 2007 01:08 PM
> *To:* daniel.fink_at_optimaldba.com
> *Cc:* oracle-l_at_freelists.org
> *Subject:* Re: REDO LOG Concepts
>
>
> Hi Daniel,
>
> I did not try for other processes. But will the rm command in OS command
> queue? Is there any posibility to rollback the delete when the instance is
> open? And if at all it is possible will the commited transactions be
> reclaimed?
>
> Deepak
>
>
> On 5/17/07, Daniel W. Fink <daniel.fink_at_optimaldba.com> wrote:
> >
> > This occurs as at least one of the Oracle processes (LGWR, others?)
> > still has the redo log open. You can rm it and it will 'disappear' from the
> > file list, but as it is still open by LGWR. so when the log buffer is
> > flushed and written by LGWR, it is written to the file that LGWR still has
> > open. Once you shutdown the instance, LGWR terminates and lets go of the
> > file, which is then 'officially' rmed. When the instance is restarted, the
> > process(es) attempt to open the file, but cannot as it has been deleted.
> >
> > --
> > Daniel Fink
> >
> > Oracle Performance, Diagnosis and Training
> >
> > OptimalDBA http://www.optimaldba.com
> > Oracle Blog http://optimaldba.blogspot.com
> >
> > Join me at Miracle Scotland DB Forum!http://www.miracleltd.com/index.asp?page=167&page2=343
> >
> >
> >
> > DBA Deepak wrote:
> >
> > Hi All,
> >
> > As we know when we issue a COMMIT the log buffer content is flushed to
> > the online redo log file before the "Commit complete" status is returned to
> > the user. Please correct me if I am wrong.
> >
> > I have the following scenario...
> >
> > SQL> select member from v$logfile;
> >
> > MEMBER
> > --------------------------------------------------------------------------------
> >
> > /u04/oradata/BIDWDB01/redo03.log
> > /u04/oradata/BIDWDB01/redo02.log
> > /u04/oradata/BIDWDB01/redo01.log
> >
> > SQL> !rm /u04/oradata/BIDWDB01/redo01.log
> >
> > SQL> !rm /u04/oradata/BIDWDB01/redo02.log
> >
> > SQL> !rm /u04/oradata/BIDWDB01/redo03.log
> >
> >
> > SQL> connect scott/oracle
> > Connected.
> > SQL> update emp set ename=ename;
> >
> > 14 rows updated.
> >
> > SQL> commit;
> >
> > Commit complete.
> >
> > SQL> commit;
> >
> > Commit complete.
> >
> > SQL> conn / as sysdba
> > Connected.
> > SQL> shutdown immediate
> > Database closed.
> > Database dismounted.
> > ORACLE instance shut down.
> >
> >
> > SQL> startup
> > ORACLE instance started.
> >
> > Total System Global Area 4479516672 bytes
> > Fixed Size 1984504 bytes
> > Variable Size 905975816 bytes
> > Database Buffers 3556769792 bytes
> > Redo Buffers 14786560 bytes
> > Database mounted.
> > ORA-00313: open failed for members of log group 1 of thread 1
> > ORA-00312: online log 1 thread 1: '/u04/oradata/BIDWDB01/redo01.log'
> >
> >
> >
> >
> >
> > -----------------------
> >
> > My question is even after deleting all the online redo log files how did
> > Oracle returned the Commit complete status to the user? What happened to the
> > log buffer data flush?
> >
> > I am using 10.2.0.2 on Solaris 9 (64-bit)
> >
> >
> > Regards,
> >
> > Deepak
> >
> >
> >
>
>
> --
> Regards,
>
> Deepak
> Oracle DBA
>

-- 
Regards,

Deepak
Oracle DBA

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