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Message Posted: Fri, 26 Sep 2003 @ 14:25:28 GMT

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When you change a primary index in Teradata the records will always be deleted and reinserted; this is because a change in PI invariably result in a change to the Amp, cylinder or block where the record is stored and so the record must be moved to maintain it's order within the ranks.

The reason why Teradata is so slow with updates is because it performs them on a record by record basis. This means having to perform a read-delete-move-write for every record and requires a journal entry for each modification. If you use the delete/insert approach then Teradata is able to handle the process in bulk and the number of journaling entries shifts from the record level to the table level.

Hope this helps,

Jason

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