Re: Update Statements and Exadata
- From: Martin Berger <martin.a.berger@xxxxxxxxx>
- To: Coskan Gundogar <coskan@xxxxxxxxx>
- Date: Sun, 9 Dec 2012 14:45:37 +0100
I'd say, for an update you allways need blocks in buffer cache,
whereas for a select Cells can deliver prepared data already - so there is
no block structure anymore.
Now my guesswork starts:
Someone at Oracle decided "if only one process is running the update, it
need to get all the blocks (for update) into buffercache at all - so don't
let double the work, which would be: first transfer data-only
(serial_direct) - afterwards transfer the blocks (sequential read?)
For parallel processing the thing might be different: the parallel
processes wich consume the data might be delivered via offloading, but
those parallel processes which do the update itself has to go via
buffer_cache/conventional.
Again, just a guesswork; I'd be hope to get detailled insights myself :-)
Martin
On Sun, Dec 9, 2012 at 2:32 PM, coskan gundogar <coskan@xxxxxxxxx> wrote:
> That is alright but what is changing with the undo management when issued
> parallel so it can be offloaded as if i just select instead of update
> regardless of degree it is always ofloading
>
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