From description, it looks like : 10949 event has same impact as the parameter _serial_direct_read. Its likely that, the behavior of parameter "_serial_direct_read" coupled with "_small_table_threshold" parameter in 11gR2 triggers the use direct path reads. Both parameters were present in earlier versions of Oracle, but in 11gR2 the behavior is different. You may like to have a look at following blog by Charles Hooper and testcase posted by Kyle Hailey in comments section. http://hoopercharles.wordpress.com/2010/06/17/_small_table_threshold-parameter-and-buffer-cache-what-is-wrong-with-this-quote/ Regards, Saurabh Manroy http://smanroy.wordpress.com On Tue, Aug 30, 2011 at 12:27 PM, D'Hooge Freek <Freek.DHooge@xxxxxxxxx>wrote: > Pawel, > > In 11.2, the db has the possibility to send the blocks from a full table > scan directly to the server process memory (pga), bypassing the buffer > cache. > This would explain the higher "db direct read" you are seeing. > > I also have the impression that this can cause a higer pga usage on 11g > then on 10g. > > > Regards, > > > Freek D'Hooge > Uptime > Oracle Database Administrator > email: freek.dhooge@xxxxxxxxx > tel +32(0)3 451 23 82 > http://www.uptime.be > disclaimer: www.uptime.be/disclaimer > > -----Original Message----- > From: oracle-l-bounce@xxxxxxxxxxxxx [mailto:oracle-l-bounce@xxxxxxxxxxxxx] > On Behalf Of Pawel Smolarz > Sent: dinsdag 30 augustus 2011 12:05 > To: ORACLE-L > Subject: performance issue after upgrade from 10.2.0.5 to 11.2.0.2 > > Hi, > I upgraded database from 10.2.0.5 to 11.2.0.2.2 on AIX 5.3 platform > without problem. Everything works perfectly. > During performance testing we noticed much slower queries. > We have two databases, one 10.2.0.5 and 11.2.0.2. Both databases are the > same (data and parameters). The first 10g based on physical lun, second > 11g based on snapshot from physical lun. > After investigation I found that 11g execution plan is different than on > 10g. OK. No problem. I saved execution plan from 10g (sqlset) and loaded > to 11g, and on both databases execution plan is the same. > > But. On 11g I see that optimizer prefers sequential read and db direct > read than scattered read (10g). This causes the query execution time is > longer- ~ 4x. Maybe the reason is snapshot??. > We solved this problem by setting the events '10949', but maybe someone > knows where is the cause. > > -- > Pozdrawiam / Regards, > Paweł Smolarz > > > Nordea Bank Polska S.A. z siedzibą w Gdyni, ul. Kielecka 2, 81-303 Gdynia, > wpisaną do Rejestru Przedsiębiorców Krajowego Rejestru Sądowego pod > numerem: 0000021828, > dla której dokumentację przechowuje Sąd Rejonowy Gdańsk - Północ w Gdańsku, > VIII Wydział Gospodarczy Krajowego Rejestru Sądowego, > o kapitale zakładowym i wpłaconym w wysokości: 277.493.500,00 złotych, > NIP: 586-000-78-20, REGON: 190024711-- > //www.freelists.org/webpage/oracle-l >