Re: What's the cost of snapshots ?

Frederic Payant wrote:
>
> Hi,
>
> How can I compute the cost of snapshots - in CPU, network, disk I/O
> terms ?
>
> Regards
> Frederic PAYANT - junior DBA ;-)

The snapshot is typically sourced in one of two ways - a full copy at regular intervals versus recording changes in the source and applying them to the snapshot.

In the former case, the overhead is simply the same as a large scale insert - you can schedule these in quiet times but of course, your snapshot is typically more out-of-date compared to the source.

With the incremental (or "fast" refresh), there is an overhead on the source table since every change is logged. Whilst there are no hard and fast rules, typically overhead is about 5-10% for inserts/updates/deletes on the source.

hth
connor

-- 
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Connor McDonald

http://www.oracledba.co.uk

"Some days you're the pigeon, some days you're the statue..."