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RE: Query Database while shutdown in progress

From: Randy Johnson <randyjo_at_sbcglobal.net>
Date: Thu, 28 Jun 2007 18:29:45 -0500
Message-ID: <004301c7b9dc$36ddfcd0$6701a8c0@scraunch>


Okay, I stand corrected. That's what happens when you reply from memory.  

My bad.    

CHECKPOINT TUNING AND ERROR HANDLING  

  1. What is a Checkpoint?

   A Checkpoint is a database event which synchronizes the modified data blocks in memory with the datafiles on disk. It offers Oracle the means for ensuring the consistency of data modified by transactions. The mechanism of writing modified blocks on disk in Oracle is not synchronized with the commit of the corresponding transactions.  

    A checkpoint has two purposes: (1) to establish data consistency, and (2) enable faster database recovery. How is recovery faster? Because all database changes up to the checkpoint have been recorded in the datafiles, making it unnecessary to apply redo log entries prior to the checkpoint. The checkpoint must ensure that all the modified buffers in the cache are really written to the corresponding datafiles to avoid the loss of data

    which may occur with a crash (instance or disk failure).   

    Oracle writes the dirty buffers to disk only on certain conditions:  

    A checkpoint is realized on five types of events:  

    During a checkpoint the following occurs:

From: oracle-l-bounce_at_freelists.org [mailto:oracle-l-bounce_at_freelists.org] On Behalf Of Jared Still
Sent: Thursday, June 28, 2007 1:46 PM
To: randyjo_at_sbcglobal.net
Cc: oracle-l
Subject: Re: Query Database while shutdown in progress

On 6/27/07, Randy Johnson <HYPERLINK
"mailto:randyjo_at_sbcglobal.net"randyjo_at_sbcglobal.net> wrote:   

BTW, unless I'm mistaken, checkpoints occur automatically at the least every 3 seconds.  

Gee, I hope not.

LGWR on the other hand... :)

-- 
Jared Still
Certifiable Oracle DBA and Part Time Perl Evangelist 



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Received on Thu Jun 28 2007 - 18:29:45 CDT

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