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Message Posted: Wed, 21 May 2008 @ 09:22:19 GMT


     
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Subj:   Re: Dirty read during UPDATE question
 
From:   Walter, Todd A

If you are on a fairly current release, the only reason that Teradata will do merge delete, followed by merge will be if you are updating the primary index. If you see that plan, then you will be subject to having those rows not visible to locking for access readers during the period when they have been deleted but not merged back in.

A technique used to avoid this is to place LOCKING FOR EXCLUSIVE on the update statement. This will block the locking for access readers and cause them to wait until the update is complete but will avoid the invisibility of the records.



     
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