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Re: Oracles streams stability for 9.2.0.5

From: <jkundu_at_yahoo.com>
Date: 5 May 2006 06:52:51 -0700
Message-ID: <1146837171.834175.254170@j33g2000cwa.googlegroups.com>


I am not sure why you think logging the supplemental information into the undo results in a double penalty. Every block change in Oracle creates a before image (undo), and an after-image (redo). Supplemental information always pertain to the before-image (since the columns are not going to change), and is only logged in the before-image part (undo).
Having said that, supplemental logging does add an overhead, especially for tables that do not have any unique/primary constraints defined. Note if constraint maintenance overhead is the reason that you do not want to define such a constraint, you can always define RELY constraints to direct the supplemental logging mechanism to log a subset of columns that uniquely identify the row, although there is no unique/primary constraints being maintained on the table.

Regards
-Joydip Received on Fri May 05 2006 - 08:52:51 CDT

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