dynamic performance table

Please let me know when ORACLE updates the dynamic performance tables, especially V$SYSSTAT.

I tried to check up whether a SQL statement requires only the use of a memory or requires the use of a disk.

I restarted ORACLE instance, and issued following SQL statement.

   select * from tbl1 order by key1;

And then, I issued the following query in order to list the value of sorts(memory) and sorts(disk).
  select name, value from v$sysstat

     where name in ('sorts (memory)','sorts (disk)');

And I get the information as follows:

  NAME                                                                  VALUE
  ---------------------------------------------------------------- ----------
  sorts (memory)                                                            0
  sorts (disk)                                                              0

Why? Why are both sorts(memory) and sorts(disk) all zero? Maybe I checked V$SYSSTAT before ORACLE updates V$SYSSTAT.

But I don't know when ORACLE updates V$SYSSTAT. Please e-mail me and tell me exact timing.

Thanks very much in advance.

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Touju FUJII  tfujii_at_zoo.ncl.omron.co.jp
    OMRON Corp. Fuzzy Technology Business Promotion Division, Kyoto


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