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Home -> Community -> Mailing Lists -> Oracle-L -> RE: cpu time and query column in tkprof output
I totally agree with that but the first sql is faster and it also has
better latch statistics, so i conclude that it is also more scalable.
The only problem with it is that it has more number of logical reads.
RUN2 is the faster sql. As seen it has better latch numbers. But it has more logical reads.
NAME RUN1 RUN2DIFF
-------------------------------------------------- ---------- ---------- ---------- LATCH.cache buffers lru chain 32883 25895 -6988 LATCH.enqueues 16234 8912 -7322 LATCH.row cache objects 57411 32360 -25051 LATCH.library cache 100992 55926 -45066 LATCH.cache buffers chains 811950 595768-216182
=20
-----Original Message-----
From: oracle-l-bounce_at_freelists.org
[mailto:oracle-l-bounce_at_freelists.org] On Behalf Of Cary Millsap
Sent: Thursday, February 03, 2005 3:02 PM
To: zoran_martic_at_yahoo.com; Yasin Baskan; oracle-l_at_freelists.org
Subject: RE: cpu time and query column in tkprof output
> Your first SQL can be faster but it is less scalable
> and can cause ELAPSED time to be worse if you have
> very busy system.
Absolutely true. To be really picky with the words, it can cause CPU =3D
time to
be worse, too, if you have a busy system. It's because Oracle's =3D
busy-wait
strategy for latch acquisition is very CPU intensive. The longer a =3D
process
has to wait for a latch to become available, the more CPU it will burn =
=3D
while
busy-waiting.
Cary Millsap
Hotsos Enterprises, Ltd.
http://www.hotsos.com
* Nullius in verba *
Upcoming events:
- Performance Diagnosis 101: 2/23 Houston, 3/16 Salt Lake City - SQL Optimization 101: 2/7 Dallas - Hotsos Symposium 2005: March 6-10 Dallas - Visit www.hotsos.com for schedule details...
-----Original Message-----
From: oracle-l-bounce_at_freelists.org =3D
[mailto:oracle-l-bounce_at_freelists.org]
On Behalf Of Martic Zoran
Sent: Thursday, February 03, 2005 4:55 AM
To: yasbs_at_kocbank.com.tr; cary.millsap_at_hotsos.com; =3D
oracle-l_at_freelists.org
Subject: RE: cpu time and query column in tkprof output
Hi Yasin,
These are LATCH stats and not STAT stats.
Latch statistics are very important to predict which SQL will behave better when running in multiuser environment, with many processes doing the same or similar SQL's causing them to wait/lock/block on these latches.=3D20
Stats are showing more about what you needed to perform and partially on what you spend your pure CPU time.
Your first SQL can be faster but it is less scalable and can cause ELAPSED time to be worse if you have very busy system.
You should test it in real case scenario while having other things running (ideally the production :)
Regards,
Zoran
> Here are all the stats. Yes the execution plans are
> different. What i am
> trying to do is to re-write the sql for better
> performance. I re-write
> the sql ang get lower number of logical reads, but
> lose in other areas
> as i mentioned.
>=3D20
>=3D20> DIFF
> NAME =3D20
> RUN1 RUN2
=3D09
__________________________________=3D20
-- http://www.freelists.org/webpage/oracle-l -- http://www.freelists.org/webpage/oracle-l -- http://www.freelists.org/webpage/oracle-lReceived on Thu Feb 03 2005 - 08:47:10 CST
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