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Message Posted: Mon, 08 Jan 2002 @ 00:42:07 GMT


     
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Subj:   Re: Block everybody with ALTER TABLE
 
From:   Todd A. Walter

re C: One advantage of ALTER TABLE is that it does NOT write a journal record for each row. It has separate block level restart logic so it can be fast and recoverable.

re C: INSERT SELECT is also a way to perform this operation. However, it requires two perm copies of the data and one spool copy. ALTER TABLE works a chunk at a time and does not require three copies of the table, pretty important for the really big ones. INSERT SELECT does not require journalling either as long as the new target table is empty and the IS is done as a standalone transaction.

Answer to original question: The AccessRights lock is the likely culprit. The reason it is necessary is that the columns being dropped MIGHT have had column level access rights defined on them that have to be removed. Those column level rights may be anywhere in the AccR table as the PI is Looks like a more efficient implementation of that removal operation needs to be on the list...



     
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