RE: Operations that perform multiblock I/O and cluster factor

I'm pretty sure you are correct - only FTS and FFS will perform "db file scattered read" (reference:
http://download.oracle.com/docs/cd/B10501_01/server.920/a96533/instance_ tune.htm#15945). There are other multi-block I/Os though, for example direct path reads & writes to temp, but those show up under their own wait events, not "db file scattered read", and they do not occur on behalf of an index range scan. I think your co-worker is wrong and if s/he's going to make such claims in contradiction to the documentation - the burden of proof is on him so ask him/her to show you a 10046 trace file with "db file scattered read" wait events coming from an INDEX RANGE SCAN, or some other proof.  

Regards,
Brandon  

From: oracle-l-bounce_at_freelists.org
[mailto:oracle-l-bounce_at_freelists.org] On Behalf Of Josh Collier    

Are there any other access paths that are served by multiblock I/O? My co-worker contends: If the range scan is not a full scan, the query optimizer will decide whether to use a scattered read depending on the fraction of rows in the scan and the cluster factor of the index.

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