Increasing CPU on every execution of an anonymous block sent from WebLogic
- From: "Baumgartel, Paul" <paul.baumgartel@xxxxxxxxxxxxxxxxx>
- To: oracle-l@xxxxxxxxxxxxx
- Date: Tue, 20 Mar 2007 16:04:32 -0000
Oracle 9.2.0.8 on Solaris 8.
I've asked development to rewrite Java code that issues SQL with literals so
that it uses binds. The new code dynamically constructs an anonymous PL/SQL
block with binds, binds values to it, and executes it. The block consists
solely of insert statements. I am aware that this would be better to implement
this as a packaged procedure, but because this is a heavily-used function of a
critical system, development is not willing to move the code from one tier to
another.
Each business transaction executes this block a few hundred times.
In testing we found that transactions using this code run for over 100 seconds,
at which point WebLogic times them out. (In the test, the
dynamically-constructed PL/SQL block is identical every time.) The same code
implemented with literals in its dynamic PL/SQL anonymous blocks performs just
fine.
Analysis of the trace files for the bind-variable version reveals that the CPU
time to EXEC the anonymous block (and, to a lesser extent, its constituent
INSERT statements) steadily increases. The first time through the CPU time is
about 0.02 second. By the last execution before the timeout, the CPU time is
just about 1.0 second. Interestingly, the logical I/O stats for each execution
are quite low (<100 current reads and consistent reads) and quite consistent.
We've made a rough copy of the anonymous block and run it several hundred times
from SQL*Plus; this setup doesn't show the increasing CPU time. It's not an
exact copy of the Java code, so not conclusive, but I wonder if it's possible
that interaction between Oracle and WebLogic, maybe in getting the bind
variable values, is somehow involved here.
Has anyone seen such behavior? Any suggestions?
Thanks in advance.
Paul Baumgartel
CREDIT SUISSE
Information Technology
DBA & Admin - NY, KIGA 1
One Madison Avenue
New York, NY 10010
USA
Phone 212.538.1143
paul.baumgartel@xxxxxxxxxxxxxxxxx
www.credit-suisse.com
_____
From: oracle-l-bounce@xxxxxxxxxxxxx [mailto:oracle-l-bounce@xxxxxxxxxxxxx] On
Behalf Of Jared Still
Sent: Monday, March 19, 2007 2:40 PM
To: Kerber, Andrew W.
Cc: robertgfreeman@xxxxxxxxx; oracle-l@xxxxxxxxxxxxx
Subject: Re: Why an organization would need an enterprise DB team
On 3/19/07, Kerber, Andrew W. <Andrew.Kerber@xxxxxxx
<mailto:Andrew.Kerber@xxxxxxx> > wrote:
I think it would be more accurate to say that developers don't really have time
to figure out how the database really works, and dba's don't really have time
to figure out how the developers are programming.
Maybe, maybe not. A developer does not need to know in depth how the database
works, but do need to know how certain features work, such as undo and redo.
A developer should know why it is bad to do simple DML in a loop, and why
issuing COMMIT frequently is a bad idea.
If they are unable/unwilling to learn, then they need to trust the DBA.
That trust works both ways of course.
--
Jared Still
Certifiable Oracle DBA and Part Time Perl Evangelist
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