ORACLE 10949 EVENT

Maclean Liu(刘相兵

kcl.c@10949
A "select ... for update" query shows slow performance and
following three conditions meet
* query run full table scan against large table and run serially (not PQ)
* query use direct path reads against the table
   followed by "db file sequential read" operations.
   You can check this by "alter session set events 'sql_trace wait=true';
   and examine generated SQL trace file.
* The query selects a large number of rows and updates many of them
* Setting event 10949 level 1 to disable the direct reads
   shows improved performance.

Workaround
  Set event 10949.
  eg: alter session set events '10949 level 1';

  The setting of event 10949 to disable direct path reads has shown an
immediate and dramatic performance improvement for GE Capital without their
having to increase buffer cache size.



alter system set events '10949 trace name context forever,level 1';

zyclove201305

请问，
怎样查看是否设置了10949事件呢？

typ281

SQL>  alter session set events '10949 level 1';

Session altered.

SQL> set serveroutput on
declare
  event_level number;
  begin
  for i in 10000..10999 loop
     sys.dbms_system.read_ev(i,event_level);
     if (event_level > 0) then
      dbms_output.put_line('Event '||to_char(i)||' set at level '||
                             to_char(event_level));
     end if;
  end loop;
end;
/
Event 10949 set at level 1