RE: Statspack ratios help
- From: Joseph Amalraj <joseph@xxxxxxxxxxxxxx>
- To: cary.millsap@xxxxxxxxxx, terrysutton@xxxxxxx, oracle-l@xxxxxxxxxxxxx
- Date: Thu, 8 Jun 2006 04:51:07 -0700 (PDT)
Can you suggest some books and other resources to learn about
profiling.
Thanks
Joseph Amalraj
Cary Millsap <cary.millsap@xxxxxxxxxx> wrote:
> though the fact that almost all of your parses are soft is a good
thing
Man, I was onboard 'til that last sentence. :)
I think the right statement about this is the same one Terry used in his
first paragraph. Rephrasing slightly, I'd say, "It might be good. But it
might not. You can't tell by looking only at this."
To me (normally pessimistic), so many parse calls are a red flag
indicating that the application is doing something stupid: either
parsing inside a loop, or closing and reopening cursors too often, or
doing the 2-tier thing of disconnecting and connecting instead of the
3-tier thing of sharing Oracle sessions.
I think Terry's point is that having a bunch of soft parses probably
beats having the same number of hard parses, but my point is that what
we're seeing here is probably way short of good enough.
My favorite close-enough definition of "soft parse" is this: "How the
Oracle kernel handles a parse call that the application should never
have made in the first place." Think about it...
One final point: I HATE doing analysis with wait-wait-don't-tell-me data
like the basis of this thread. To Jonathan's point, you simply can't
tell from data like this what the performance IMPACT of the change is
going to be. If we were looking at profiles instead of Statspack data,
then we'd be able to tell exactly how many seconds per business task
this behavior is costing someone.
That may sound self-serving because I'm a profiler company guy, but the
factual basis behind this statement is WHY I have dedicated my career to
becoming a profiler company guy.
Cary Millsap
Hotsos Enterprises, Ltd.
http://www.hotsos.com
Nullius in verba
Hotsos Symposium 2007 / March 4-8 / Dallas
Visit www.hotsos.com for curriculum and schedule details...
-----Original Message-----
From: oracle-l-bounce@xxxxxxxxxxxxx
[mailto:oracle-l-bounce@xxxxxxxxxxxxx] On Behalf Of Terry Sutton
Sent: Tuesday, June 06, 2006 8:04 PM
To: oracle-l@xxxxxxxxxxxxx
Subject: Re: Statspack ratios help
Sandeep,
You've gotten some comments which may be confusing. I'll have to
disagree
with the concept that "a 100% buffer cache hit ratio is bad". That's
not
true. A 100% BCHR is not bad. Nor is it good. That's why wise folk
tell
you not to use ratios to judge/improve performance. The ratio is mostly
irrelevant.
What you want to look at is the section of Statspack that is half a page
below these ratios-- the Wait Event and CPU usage statistics. Is your
system spending a large amount of time waiting? If it's not waiting, is
the
CPU usage high (relative to the number of CPUs you have). If the answer
to
these questions is no, then you don't have a system-wide problem. But
that
doesn't mean that you might not have problems with individual processes,
which may not show up in system-wide statistics. Are your users
complaining? Is your application sufficiently fast? If something is
running slowly, you want to concentrate on that process (which is where
you
use 10046 traces and such, as someone mentioned).
But the ratios below don't tell you what you need to know (though the
fact
that almost all of your parses are soft is a good thing).
--Terry
> Hi,
>
> I am running OLTP system on Oracle 10.2 and J2EE weblogic.
>
> I am getting some ratios as:
>
> Load Profile Per Second Per
Transaction
> ~~~~~~~~~~~~ ---------------
---------------
> Redo size: 156,162.18
3,020.55
> Logical reads: 26,407.64
510.79
> Block changes: 904.27
17.49
> Physical reads: 0.39
0.01
> Physical writes: 34.01
0.66
> User calls: 5,863.32
113.41
> Parses: 981.47
18.98
> Hard parses: 0.01
0.00
> Sorts: 16.97
0.33
> Logons: 5.54
0.11
> Executes: 1,085.95
21.00
> Transactions: 51.70
>
>
> Rollback per transaction %: 44.17
> Buffer Nowait %: 100.00 Redo NoWait %: 99.97
> Buffer Hit %: 100.00 In-memory Sort %: 100.00
> Library Hit %: 100.00 Soft Parse %: 100.00
> Execute to Parse %: 9.62 Latch Hit %: 99.88
> Parse CPU to Parse Elapsd %: 69.06 % Non-Parse CPU: 91.60
>
> With 100% soft parse, execute to parse ratio is so low. Is it bad, how
> I can I improve it?
>
> I see rollback per transaction as 44.17. We are using Hibernate that
> generates database mapping and produces most of the SQLs. How can I
> invetigate further? But I doubt if application is doing some big time
> rollbacks.
>
> Thanks for help
>
> Sandeep
> --
> //www.freelists.org/webpage/oracle-l
>
>
>
>
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