Hi, dba friends:
I trussed some process execution in my system, and get result like:
oracle@main-db1$truss -c -p 3995
^Csyscall seconds calls errors
read .47 6963
write .48 6555
lseek .01 402
kill .00 2
times .61 25964
semsys .01 44
sigprocmask .00 92
context .00 23
yield .00 52
setitimer .01 46
pread .04 162
---- --- ---
sys totals: 1.63 40305 0
usr time: 11.89
elapsed: 129.88
Also, from somewhere , i see someone's trick about xdual vs dual, and i did a
benchmark:
with dual:
SQL> select * from v$mystat where statistic#=12;
SID STATISTIC# VALUE
---------- ---------- ----------
17 12 19907
Elapsed: 00:00:00.00
SQL> declare mydate date;
2 begin for x in 1..1000000 loop select sysdate into mydate from dual; end loop;
end;
3 /
PL/SQL procedure successfully completed.
Elapsed: 00:05:32.08
SQL> select * from v$mystat where statistic#=12;
SID STATISTIC# VALUE
---------- ---------- ----------
17 12 39830
and with Xdual:
select * from v$mystat where statistic#=12;
SID STATISTIC# VALUE
---------- ---------- ----------
15 12 7
declare mydate date;
begin for x in 1..1000000 loop select sysdate into mydate from xdual; end loop; end;
/
PL/SQL procedure successfully completed.
Elapsed: 00:03:34.00
select * from v$mystat where statistic#=12;
SID STATISTIC# VALUE
---------- ---------- ----------
15 12 12822
Time elapsed reduced about 40%, and cpu utilization reduced from 39830 to
12805.(less than half of the original value).
I wonder if i can really replace the public synonym dual with my dual, I can
reduce cpu usage significantly, right? But has anyone did this trick in production?
any experience?
Thanks.
Regards
zhu chao
msn:[EMAIL PROTECTED]
www.cnoug.org(ChinaOracle User Group)
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