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Home -> Community -> Mailing Lists -> Oracle-L -> Re: snapshots
At 10:06 AM 1/12/01 -0800, you wrote:
>hi list
>
>would any refresh of a snapshot fire a query against the base table?
>
> i think its supposed to go against the mlog$ table of the base table. we
>have a situation where there is a poor-performing query that is fired at
>exact intervals accessing the base table and no application seems to be
>firing it?
The mlog$ table only contains a couple of fields, one of which is the ROWID of the affected record, and another is the dml operation (insert, delete, update). I'd assume that the snapshot update uses this info to go get the affected record (unless it's a delete) from the base table.
This is weird when you think of it. It implies that the snapshot process is able to get "old" information, i.e. the record from before the delete, so that it can grab the PK info. Or am I missing something?
Dennis Taylor
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