Re: REDO LOG Concepts

Thanks a lot Daniel, you are correct as far as the "rm" UNIX command is concerned. I checked the diskspace usage before and after shutdown. UNIX is only releasing teh space after the shutdown command is issued.

Deepak

On 5/17/07, Daniel W. Fink <daniel.fink_at_optimaldba.com> wrote:
>
> Deepak,
>
> I'll have to leave the detailed explanations of file systems, files and
> i-nodes to the unix gurus, and any mistakes are likely due to my inexact
> understanding of these concepts.
>
> The rm command is not placed in a queue, but works to remove file system
> information about the file you are removing. However, any process that
> still has the file open (or locked if you prefer this way of thinking of
> it) still has that file system information. It can still read from and
> write to that file, but any process that attempts to open the file will
> not find the file system information and so that attempt fails. Once all
> of the processes that have the file open, all file system information
> about that file is gone.
>
> In your scenario, the update is committed, so it cannot be rolledback. A
> SHUTDOWN NORMAL, IMMEDIATE or TRANSACTIONAL will have no uncommitted
> transactions within the database (everything is either committed or
> rolled back...no in between).
>
> Let's say you issued a SHUTDOWN ABORT after the update, then the
> database might contain uncommitted transactional data. Upon instance
> startup, it will attempt to rollback any uncommitted transactions by
> reading the redo log...but you've deleted the redo logs, therefore all
> the information to rollback the transaction is gone.
>
> --
> Daniel Fink
>
> Oracle Performance, Diagnosis and Training
>
> OptimalDBA http://www.optimaldba.com
> Oracle Blog http://optimaldba.blogspot.com
>
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> http://www.miracleltd.com/index.asp?page=167&page2=343
>
>
> DBA Deepak wrote:
> > 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
> >
> >
>
>

-- 
Regards,

Deepak
Oracle DBA

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