Re: How to calibrate the CBO

One more remark: According to the statspack reports, time is being consumed here by "db file sequencial read". This phenomenal knowledge does not buy me anything, though.

What is more interesting: Since system statistics are being collected, the corresponding view SYS.AUX_STATS$ reports that a sinble block access takes almost 3x as long as a MBRC, which surprises me a lot (8 msec vs. 3 msec). Note: as I understand, Oracle can't tell anything about real physical access; data often comes from the storage cache, which explains the low values.

The Performance Tunig Pack of the OEM shows also very clear that "db file sequencial read" is always a predominant wait event (in terms of waited time), no matter what query is running, compared to FTS. I still feel challenged to better understand why.

Thanks again
Rick Denoire Received on Sun Feb 08 2004 - 17:44:19 CST