Yes, it does say when dynamic sampling is evaluated or executed.
1st example is where dyn sampling is used:
---------------------
SINGLE TABLE ACCESS PATH
*** 2003-12-31 17:25:07.521
** Performing dynamic sampling initial checks. **
** Dynamic sampling initial checks returning TRUE (level = 4).
*** 2003-12-31 17:25:07.581
** Generated dynamic sampling query:
query text : SELECT /*+ ALL_ROWS IGNORE_WHERE_CLAUSE */ NVL(SUM(C1),0),
NVL(SUM(C2),0) FROM (SELECT /*+ NOPARALLEL("T") */ 1 AS C1, 1 AS C2 FROM "T"
"T") SAMPLESUB
*** 2003-12-31 17:25:07.631
** Executed dynamic sampling query:
level : 4
sample pct. : 100.000000
actual sample size : 1
filtered sample card. : 1
orig. card. : 409
block cnt. : 5
max. sample block cnt. : 32
sample block cnt. : 5
min. sel. est. : -1.0000
** Using dynamic sampling card. : 1
TABLE: T ORIG CDN: 1 ROUNDED CDN: 1 CMPTD CDN: 1
Access path: tsc Resc: 3 Resp: 3
BEST_CST: 4.00 PATH: 2 Degree: 1
---------------------
Second example is where dynamic sampling is considered, but eventually not
used
---------------------
** Performing dynamic sampling initial checks. **
** Dynamic sampling initial checks returning TRUE (level = 1).
** Not using dynamic sampling: max. blk. (1) count too low.
---------------------
When dyn sampling isn't even considered, then there'll be no lines about
dynamic sampling in 10053 trace (except few parameter values which which are
always written to trace).
Tanel.
----- Original Message -----
To: "Multiple recipients of list ORACLE-L" <[EMAIL PROTECTED]>
Sent: Wednesday, December 31, 2003 4:59 PM
> Wolfgang,
> I don't have 9i available at the moment so I can't test this. Just
wondering if
> a 10053 trace shows you if the statistics it is using are gathered from
dynamic
> sampling.
>
> Henry
>
>
> -----Original Message-----
> Wolfgang Breitling
> Sent: Tuesday, December 30, 2003 6:24 PM
> To: Multiple recipients of list ORACLE-L
>
>
> The CBO will do dynamic sampling automatically provided the conditions are
> met. The conditions that need to be met depend on the dynamic_sampling
> initialization parameter in effect for the session. The default is 1 which
> practically disables dynamic sampling. 0 will totally disable it but IMHO
> the conditions for dynamic_sampling=1 are so rare (in practice) that one
> can regard it as off.
> BTW, even if the CBO goes to dynamic sampling that does not guarantee that
> it will use the statistics it did gather this way.
>
> At 03:24 PM 12/30/2003, you wrote:
> >Tanel,
> >
> >I know the values, you are missing my question ... let me re-phrase it
..
> >
> >1. To have CBO use dynamic sampling do you have to specify the hint?
> >or
> >2. CBO will do that automatically?
> >
> >Just to let you know, Oracle 9ir2 docs main page is my home page on
> >Mozilla firebird browser and Metalink is my homepage on IE.
> >Raj
>
>---------------------------------------------------------------------------
----
> -
> >Rajendra dot Jamadagni at nospamespn dot com
> >All Views expressed in this email are strictly personal.
> >QOTD: Any clod can have facts, having an opinion is an art !
> >
> >
> >-----Original Message-----
> >Sent: Tuesday, December 30, 2003 2:44 PM
> >To: Multiple recipients of list ORACLE-L
> >
> >
> >Go to tahiti.oracle.com and search for the optimizer_dynamic_sampling
> >parameter, you'll see descriptions for it's different values there.
> >
> >Tanel.
> >--
> >Please see the official ORACLE-L FAQ: http://www.orafaq.net
> >--
> >Author: Jamadagni, Rajendra
> > INET: [EMAIL PROTECTED]
> >
> >Fat City Network Services -- 858-538-5051 http://www.fatcity.com
> >San Diego, California -- Mailing list and web hosting services
> >---------------------------------------------------------------------
> >To REMOVE yourself from this mailing list, send an E-Mail message
> >to: [EMAIL PROTECTED] (note EXACT spelling of 'ListGuru') and in
> >the message BODY, include a line containing: UNSUB ORACLE-L
> >(or the name of mailing list you want to be removed from). You may
> >also send the HELP command for other information (like subscribing).
>
> Wolfgang Breitling
> Oracle7, 8, 8i, 9i OCP DBA
> Centrex Consulting Corporation
> http://www.centrexcc.com
>
> --
> Please see the official ORACLE-L FAQ: http://www.orafaq.net
> --
> Author: Wolfgang Breitling
> INET: [EMAIL PROTECTED]
>
> Fat City Network Services -- 858-538-5051 http://www.fatcity.com
> San Diego, California -- Mailing list and web hosting services
> ---------------------------------------------------------------------
> To REMOVE yourself from this mailing list, send an E-Mail message
> to: [EMAIL PROTECTED] (note EXACT spelling of 'ListGuru') and in
> the message BODY, include a line containing: UNSUB ORACLE-L
> (or the name of mailing list you want to be removed from). You may
> also send the HELP command for other information (like subscribing).
> --
> Please see the official ORACLE-L FAQ: http://www.orafaq.net
> --
> Author: Poras, Henry R.
> INET: [EMAIL PROTECTED]
>
> Fat City Network Services -- 858-538-5051 http://www.fatcity.com
> San Diego, California -- Mailing list and web hosting services
> ---------------------------------------------------------------------
> To REMOVE yourself from this mailing list, send an E-Mail message
> to: [EMAIL PROTECTED] (note EXACT spelling of 'ListGuru') and in
> the message BODY, include a line containing: UNSUB ORACLE-L
> (or the name of mailing list you want to be removed from). You may
> also send the HELP command for other information (like subscribing).
>
--
Please see the official ORACLE-L FAQ: http://www.orafaq.net
--
Author: Tanel Poder
INET: [EMAIL PROTECTED]
Fat City Network Services -- 858-538-5051 http://www.fatcity.com
San Diego, California -- Mailing list and web hosting services
---------------------------------------------------------------------
To REMOVE yourself from this mailing list, send an E-Mail message
to: [EMAIL PROTECTED] (note EXACT spelling of 'ListGuru') and in
the message BODY, include a line containing: UNSUB ORACLE-L
(or the name of mailing list you want to be removed from). You may
also send the HELP command for other information (like subscribing).
