Brandon, Thanks. I mean if there are statistics already on the table : then : what is the need to do more sampling : is it to take care of changes to the table since the statistics were gathered. And is it not a overhead. So would this benefit only cases where the table data changes a lot? Another question is does this affect in any way the automatic gather of statistics done by job GATHER_STATS_JOB in dba_scheduler_jobs. IS there a way to disable it using dba account or can it be disabled as SYS only. Apart from setting optimizer_dynamic_sampling=1 and disabling GATHER_STATS_JOB : do I need to do any disable to have control over statistics. Thanks --- On Fri, 6/26/09, Allen, Brandon <Brandon.Allen@xxxxxxxxxxx> wrote: From: Allen, Brandon <Brandon.Allen@xxxxxxxxxxx> Subject: RE: ** optimizer_dynamic_sampling To: "ajoshi977@xxxxxxxxx" <ajoshi977@xxxxxxxxx>, "oracle-l@xxxxxxxxxxxxx" <oracle-l@xxxxxxxxxxxxx> Date: Friday, June 26, 2009, 5:28 PM The sampling levels are described here: http://download.oracle.com/docs/cd/B19306_01/server.102/b14211/stats.htm#sthref1118 I haven’t had any problems with auto_sample_size in 10g, but I’ve heard rumors that it’s much better/faster in 11g. Another big change to keep in mind is that in 10g histograms will be gathered by default. Regards, Brandon Privileged/Confidential Information may be contained in this message or attachments hereto. Please advise immediately if you or your employer do not consent to Internet email for messages of this kind. Opinions, conclusions and other information in this message that do not relate to the official business of this company shall be understood as neither given nor endorsed by it.