Freek D'Hooge Uptime Oracle Database Administrator email: freek.dhooge@xxxxxxxxx tel +32(0)3 451 23 82 http://www.uptime.be disclaimer: www.uptime.be/disclaimer -----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 -- //www.freelists.org/webpage/oracle-l