"Rows" statistics from STAT in trace event 10046, Oracle 11g.

Question

Hi, all!
Why "Rows" statistics in STAT are different for 10g and 11g?
I have two database with version 10g and 11g, with the same data.
I executed some pl/sql code with tracing 10046 level 8.
And I have different result when obtain raw trace.
In 10g I obtain rows statistics for all executions - Rows= 7.
In 11g I obtain rows statistics for first executions - Rows= 1. Why?
See my example:
declare
     type t_name_tbl is table of varchar2(30) index by binary_integer;
     v_name_tbl t_name_tbl;
     v_len      number := 10;
begin
     execute immediate 'alter session set timed_statistics = true ';
     execute immediate 'alter session set statistics_level=all ';
     execute immediate 'alter session set max_dump_file_size = unlimited ';
     execute immediate 'alter session set events ''10046 trace name context forever,level 8'' ';
     loop
       select cour_name bulk collect
            into v_name_tbl
           from country t
          where length(t.cour_name) = v_len;
       exit when v_len = 0;
       v_len := v_len - 1;
       for i in 1 .. v_name_tbl.count loop
         dbms_output.put_line(v_name_tbl(i));
       end loop;
     end loop;
end;Result Tkprof for Oracle 10g:
SELECT COUR_NAME
FROM
COUNTRY T WHERE LENGTH(T.COUR_NAME) = :B1
call     count       cpu    elapsed       disk      query    current        rows
Parse        1      0.00       0.00          0          0          0           0
Execute     11      0.00       0.00          0          0          0           0
Fetch       11      0.01       0.00          0         44          0           7
total       23      0.01       0.00          0         44          0           7
Misses in library cache during parse: 0
Optimizer mode: ALL_ROWS
Parsing user id: 649     (recursive depth: 1)
Rows     Row Source Operation
      7  TABLE ACCESS FULL COUNTRY (cr=44 pr=0 pw=0 time=1576 us)Result Tkprof for Oracle 11g:
SQL ID: 3kqmkg8jp5nwk
Plan Hash: 1371235632
SELECT COUR_NAME
FROM
COUNTRY T WHERE LENGTH(T.COUR_NAME) = :B1
call     count       cpu    elapsed       disk      query    current        rows
Parse        1      0.01       0.00          0          0          0           0
Execute     11      0.02       0.01          0          0          0           0
Fetch       11      0.00       0.01          3         44          0           7
total       23      0.03       0.02          3         44          0           7
Misses in library cache during parse: 1
Misses in library cache during execute: 1
Optimizer mode: ALL_ROWS
Parsing user id: 82     (recursive depth: 1)
Rows     Row Source Operation
      1  TABLE ACCESS FULL COUNTRY (cr=4 pr=3 pw=0 time=0 us cost=2 size=44 card=2)Were can I read about it?

Answer 1

Oracle 11g by default writes the execution plan (the STAT lines in the raw trace file) after the first execution of the SQL statement, while prior to 11g the execution plan is written only when the cursor is closed.
The behavior in 11g can be controlled by changing the PLAN_STAT parameter of the call that enables the trace from the default value of FIRST_EXECUTION to ALL_EXECUTIONS:
http://download.oracle.com/docs/cd/B28359_01/appdev.111/b28419/d_sessio.htm#i1010518
Charles Hooper
Co-author of "Expert Oracle Practices: Oracle Database Administration from the Oak Table"
http://hoopercharles.wordpress.com/
IT Manager/Oracle DBA
K&M Machine-Fabricating, Inc.
Edited by: Charles Hooper on Aug 9, 2010 3:33 PM
Default value on 11g is FIRST_EXECUTION, while the behavior prior to 11g is ALL_EXECUTIONS - corrected the incomplete sentence.