RE: ACID

 
Freek D'Hooge
Uptime
Oracle Database Administrator
email: freek.dhooge@xxxxxxxxx
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-----Original Message-----
From: oracle-l-bounce@xxxxxxxxxxxxx [mailto:oracle-l-bounce@xxxxxxxxxxxxx] On 
Behalf Of Goulet, Richard
Sent: woensdag 24 augustus 2011 16:31
To: Laimutis.Nedzinskas@xxxxxx; oracle-l@xxxxxxxxxxxxx
Subject: RE: ACID

I think your confusing apples with oranges.  Redo is used to create a data 
record that is as of a point in time so that you get that read consistent view 
of the data.  Logging is there so that you can recreate the changes to the data 
files during a recover operation.  Using WAL for the log records falls into 
line with Oracle's ideas on write as little as possible as infrequently as 
possible for performance enhancement.  Redo gives you the ability to show an 
existing query what the data looked like when it started without regard to if 
the change is permanent or not.  They serve very different purposes.

Richard Goulet
Senior Oracle DBA/Na Team Leader

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