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Message Posted: Thu, 02 Jul 2009 @ 08:46:52 GMT


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Subj:		Re: Explain plan for a Delete

From:		DWellman

Hi Visakh,

This explain plan step is generated for a number of statement types.

When a request is being parsed, the parser needs to read different bits of dictinary information (DDL, stats, access rights etc). For efficiency, the DBMS maintains a cache of such information. For any request where the optimiser thinks that a 'significant change' may have occurred to the table then it will flush the cache of information for the table (in this context "spoil" means flush).

A significant change includes:

- alter table

- drop/create index

- collect statistics (I think)

- certain dml's (including delete).

Hope that helps.

Cheers,

Dave

Ward Analytics Ltd: Information in motion ( www.ward-analytics.com )