Buffer Cache Hit Ratio?
What's that?
"Inka Bezdziecka" <[EMAIL PROTECTED]>
Sent by: [EMAIL PROTECTED]
10/02/2002 08:03 AM
Please respond to ORACLE-L
To: Multiple recipients of list ORACLE-L <[EMAIL PROTECTED]>
cc:
Subject: RE: Performance monitoring
Well ...
if you need short reports, look for:
1. waits
2. buffer cache hit ratio
3. dictionary hit ratio
4. library hit ratio
5. latches
6. parsing/execution ratio
7. data file i/o
8. shared pool memory distribution
9. session contention
10. session memory usage
inka
-----Original Message-----
Sent: Wednesday, October 02, 2002 7:08 AM
To: Multiple recipients of list ORACLE-L
Thak's Mark
I agreed, but they have gotten an idea to get only couple
"most important" measurements from db, because they don't want
to have a huge reports with all possible statistics. Very
understandable, but as You wrote, there isn't any absolutely top ten.
In any case, I have to do this (stupid) list, so give Your best shot,
please.
t.Jorma
Ps. I heard, that Dave Ensor from BMC, has once presented that
kind of list?
-----Original Message-----
Sent: 02 October, 2002 12:23
To: Multiple recipients of list ORACLE-L
Jorma,
Performance tuning is a complex subject. There really isn't a list of
10 things to watch for. Every system is different.
I would (attempt to) summarize tuning by these five steps:
1.) Have a capacity/performance target in mind. If you don't know
where you're going, how will you know if you have gotten there?
2.) Monitor your response times as load increases. Can you achieve
your response time target at the specified load? If so, you're done,
successful test, congratulations. If not, continue to next step.
3.) Actively monitor what's going on in the database, while it's
happening. It's always easier to see it in real time than just looking
at random StatsPack snapshots taken at 5 or 10 or 15 minute intervals.
(Not that I'm saying StatsPack shouldn't be collected. I'm just saying
don't rely on StatsPack as your only source of info about the
database.) The V$ Wait Interface is your friend. If you're not
familiar with it, go to http://www.hotsos.com/ and get Mogens Norgaard's
paper, Introducing the V$ Wait Interface. Where is the database
spending it's time? What's the bottleneck? If you identify a few
trouble sessions, you may want to dive deeper w/ some 10046 traces at
level 8 on specific sessions. You almost certainly do NOT want to do
this instance wide.
4.) Once you have some indication as to what's going on in the
database, you need to see how the system is doing overall. On most
flavors of *nix, where I'm comfortable, sar (System Activity Reporter)
is an excellent tool. Use it to determine if you have any systemwide
CPU, memory, or I/O contention. (Other OSes almost certainly have
similar utilities.)
5.) Address the biggest bottleneck. This is where it can't be
summarized in a simple step. You need to understand the bottleneck, so
that you can understand how to tune it. If may be latch contention.
Depending on the latch, it could be poorly tuned SQL, or lack of bind
variables, or simple CPU capacity limits, or a whole host of things.
I/O contention? Could be anything from poorly designed and/or
configured RAID array to poorly tuned SQL, or who knows what. Determine
the cause of the biggest bottleneck and minimize or eliminate it.
There you have it, Mark's Simplified Performance Tuning, in five easy
steps! ;-)
-Mark
On Wed, 2002-10-02 at 02:08, [EMAIL PROTECTED] wrote:
> Ave !
>
> I like to hear Your opinion about the most importat
> issues, what should be monitored from the database (8.1.7, SUN) during
> perfomance testing. The purpose in this case, is limit the
> monitoring to concern only about 10 most important ones.
>
> I have difficulties to make my mind to pick up the right ones, so
> if You had to have made similar kind of decisions or have opinions,
> please let me know.
>
> TIA
> Jorma
> -----------------------------------------------------------------
> Name: Jorma Vuorio Phone: +358-9-7180 67759
> Company: Nokia Business Infrastucture Fax: +358-9-7180 67465
> Address: P.O.Box 321, FIN-00045 NOKIA GROUP, FINLAND
> Internet: [EMAIL PROTECTED] Mobile: +358-50-486 8043
> -----------------------------------------------------------------
--
--
Mark J. Bobak
Oracle DBA
[EMAIL PROTECTED]
"It is not enough to have a good mind. The main thing is to use it
well."
-- Rene Descartes
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