UKOUG 2009 – Wednesday

Not too late an evening for me on Tuesday, though had a really informative discussion with Bryn Llewellyn on Edition Based Redefinition. He made the point that if you have two versions of the application running, you have to be careful where you users are pointing to, if they have information in their sessions. You may need to have the control over which users connect to where.

This morning I found out I had managed to pack only 1 sock. I hope no one noticed me going sockless in a freezing cold December day in Birmingham.

The first talks of the morning started quite late, but I was quite glad of it. It was a tough choice between Larry Carpenter, Bryn, and Tanel Poder. In the end I went with Tanel.

Pratical Oracle Capacity Planning – Tanel Poder

Tanel was doing essentially 4 hours of presenting today, which is amazing in itself, but when you consider the detail of the information he provides it’s just staggering.

This was a 2 hour masterclass, and it was outstanding.

Tanel is making the point about if you have many different queries going on, on your system it’s very difficult to make a mathematical model to predict the response time using queuing theory. Much easier if you have 1 unique query – queuing theory is much more practical for this.

    Data collection


awr – enable longer retention period see retention in dba_hist_wr_control

change retention with dbms_workload_repository.modify_snapshot_settings (retention => minutes)

services can be useful for finding out which application is consuming the resourcex, this can allow you to characterise your workload.

Can use V$service_stats to obtain statisics on the resources used by the various services since instance startup time.

v$servicemetric – basic metrics per service, including cpu per call, elapsed time per call, also in ASH.

Advising using dbms_application_info so you can obtain what resources each part of your application is consuming.

workload characterisation

performance/resource consumption analysis

basic utilisation forecasting

data visualisation

Tanel spent quite a large part on various examples of visualising data.

Tanel demoed his excel persheet, which allows you to automatically graph in excel various different metrics. Demo showing disk usage with a linear regression to predict futrue usage.

Tanel stating for cpu usage you might want to plot the usage at a particular time each week, as cpu flcutuates so much. You can then run linear regression on these times to make a prediction.

Gathering cpu usage data from V$osstat, and dba_hist_osstat.

Right at the start Tanel asked how many people were using queuing theory to do capacity planning. No hands went up, but I wonder how many people are doing any form of capacity planning. I found this to be a really illuminating presentation, and I’ll certainly be applying some of the ideas covered when I’m back in the office.

The lunch box was getting quite a lot of derisory comments. In particular, you could spot the Scottish person avoiding the fruit and heading straight for the KitKat. Though Pythians Paul Vallee was also rather disdainful of the fare on offer. In fact it was very interesting hearing some of the Pythian backstory. It’s an impressive thing Paul has built there (some 75 DBAs) and a fascinating story of how they have got to where they are.

The Oracle Wait Interface is useless (sometimes) – James Morle and Tanel Poder

Here they were showing that sometimes, there are problems where the Oracle wait interface can’t help. They emphasised this is the first place to look, but there are places that are not instrumented and there can be situations where Oracle itself can’t tell you what is going on, so you have to look outside the database.

Tanel showed pstack which can show which Oracle functions the process is using, while james was doing some demos with DTrace.

That was it from me, it’s been a lot shorter sojourn in Birmingham than the last few years, but it’s been great to see lots of familiar faces.


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