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On 30 May 2005 10:40:15 -0700, jasonshohet_at_gmail.com wrote:
>I read recently that if a before-image was made before an interruption
>in database processing, you use the before-image dump & simply begin
>processing again from just before the last transaction. Any
>checkpoints are irrelevant.
>
>What I don't understand is, why are checkpoints irrelevant when you did
>a before image dump? Why not begin from the last checkpoint?
>Probably part of my problem is understanding the difference between the
>before image dump and a checkpoint. I know that the checkpoint is a db
>even that suspends processing & writes data to the disk. It represents
>a moment in time when everything is OK in the db. That sounds a lot
>like a before image dump :) Maybe the checkpoint is further back in
>time (?)
>
>Thanks for any clarification
>Jason Shohet
Actually the before image is in a rollback segment (pre 9i) or in the undo tablespace (9i and higher). Rollback segments are protected by the same mechanism as the data tablespaces, which calls in for checkpoints.
-- Sybrand Bakker, Senior Oracle DBAReceived on Mon May 30 2005 - 13:06:25 CDT