RE: Capacity Planner from OEM VS Statspack

  • From: <babette.turnerunderwood@xxxxxxxxxxxxxxx>
  • To: <oracle-l@xxxxxxxxxxxxx>
  • Date: Thu, 5 Feb 2004 14:47:03 -0500

It is worse than that .....

EVERYONE has noticed that at times the performance is abysmally slow.
BUT according to all of the mainframe reporting information=20
Everything is fine... No swapping, no paging, no disk bottleneck, no =
memory problems, no CPU problems.....

For instance, full tablescan (no indexes) to update a NULL column to =
NULL
on 1 Million rows.  Can take up to three times as long at times.
BUT System people insist there is nothing being pushed at the system =
level.
The CPU is not maxed out, the disks have no bottlenecks or contention =
and there are no memory problems at this time.

There are only three things, CPU, DISK, Network.
There has to be something wrong with at least one of them to be getting =
the weird sporadic performance that we get.

It is hard to get overall picture of health of machine in MF =
environment.
We have Logical machines (LPARs) on a single physical box.
I know that I/O on other LPARs can affect our I/O, but we are told that =
there are no problems according to the system records.

The statspack information is a bonus. We have SOMETHING that we can say =
"explain this". Still waiting on explanation for a few weeks now...

Babette

-----Original Message-----
From: oracle-l-bounce@xxxxxxxxxxxxx =
[mailto:oracle-l-bounce@xxxxxxxxxxxxx] On Behalf Of Niall Litchfield
Sent: 2004-02-03 3:21 PM
To: oracle-l@xxxxxxxxxxxxx
Subject: RE: Capacity Planner from OEM VS Statspack


> I agree with Ian.... Sometimes Statspack is VERY useful..
>=3D20
> In our case the Statspack reports shows ave read times of=3D20
> 1-10ms. However we occasionally see read times of 300-700 ms.
>=3D20
> We are currently investigating what is on the slower disks,=3D20
> What systems are sharing them, and whether oracle is=3D3D20=3D20
> chaining I/O requests and giving false stats or if there=3D20
> really is a =3D3D problem. (Hey, on OS/390 mainframe system we=3D20
> don't get iostat / sar / vmstat / =3D3D
> top)
>=3D20
> This top-down approach doesn't address any SPECIFIC=3D20
> performance proble. BUT ... if we didn't have Statspack=3D20
> running periodically, we might have =3D3D missed this.
>=3D20
> - Babette

I think the interesting question here is 'If you had missed this, would
anyone care?' and its corollary 'now you have caught it, does anyone =3D
care?'.
Now I admit that I have a biased view in that all anyone ever seems to
complain to me about is 'Screen X is running slow' or 'we can't complete =
=3D
our
management reports overnight' or 'I'm not a dba so your presentation on
managing databases that I chose to attend was irrelevant' - oops sorry =
=3D
not
that last one. Almost never does anyone whinge that 'the system is =3D
slow', or
at least when they do they have a specific example in mind. As a result =
=3D
I am
definitely biased towards a view that systems don't experience problems =
=3D
-
processes do. I *suspect* that even where the *system* is slow then =3D
actually
it will be fewer than 5 processes that are killing it, but have no =3D
proof.=3D20

Niall

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