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September 2015

Measuring Tuxedo Queuing in the PeopleSoft Application Server

Why Should I Care About Queuing?

Queuing in the application server is usually an indicator of a performance problem, rather than a problem in its own right.  Requests will back up on the inbound queue because the application server cannot process them as fast as they arrive.  This is usually seen on the APPQ which is serviced by the PSAPPSRV process, but applies to other server processes too.  Common causes include (but are not limited to):

SQL for Beginners : Videos and Articles

love-sqlI’ve been saying for some time I should do some more entry level content, but it’s been kind-of hard to motivate myself. I mostly write about things I’m learning or actively using, so going back and writing entry level content is not something that usually springs to mind.

Recently I’ve got involved in a number of “grumpy old man” conversations about the lack of SQL knowledge out there. That, combined with a few people at work getting re-skilled, prompted me to get off my ass and give it a go. It’s actually quite difficult trying to get yourself into the head-space of someone who is coming fresh to the subject. You don’t want to pitch it too low and sound patronizing, but then pitching it too high makes you sounds like an elitist dick.

Histogram Tip

I’ve just responded to the call for items for the “IOUG Quick Tips” booklet for 2015 – so it’s probably about time to post the quick tip that I put into the 2014 issue. It’s probably nothing new to most readers of the blog, but sometimes an old thing presented in a new way offers fresh insights or better comprehension.

Histogram Tips

A histogram, created in the right way, at the right time, and supported by the correct client-side code, can be a huge benefit to the optimizer; but if you don’t create and use them wisely they can easily become a source of inconsistent performance, and the automatic statistics gathering can introduce an undesirable overhead during the overnight batch. This note explains how you can create histograms very cheaply on the few columns where they are most likely to have a beneficial effect.

Foreign Keys and Library Cache Locks

In this post I would like to describe a behavior of Oracle Database that, at least for me, isn’t obvious at all. Actually, it’s something that I can’t explain why it works in that way.

Let’s start by setting the scene by describing the schema I’m using for the following tests. As you can see from the image, there are three tables: one table (PARENT) that is referenced by two other tables (CHILD1 and CHILD2). Schema used for the tests In my case every table is owned by a different schema (P, C1 and C2 respectively). But, the behavior I describe is independent from that fact (i.e. it works in the same way if all tables are owned by the same schema). If you are interested, here is the SQL*Plus script I used to create them.

Speaking in Portland at NWOUG Monday Sept 14

Looking forward to speaking at

Please come join me !

I lived in Portland between 2006-2008 and love city. It will be fun being back.

8:15 – 9:00 Keynote “EBS Strategy and Roadmap” – Vanessa Paskill

Updating the Raspberry Pi Vbox Image

So one of the things I like to do is test out a lot of my python gaming code, (as far as for the coding and syntax) on my Oracle Virtualbox image of my Raspberry Pi.  Another great thing about building games on the Raspberry Pi, is a built in module called Pygame.

Oracle Midlands : Event #11 – Summary

oracle-midlandsLast night was Oracle Midlands event #11 with Chris Antognini.

The lead up to this event was not the best for me. I had been on the verge of a headache all day. By 14:00 I gave up, went home and went to sleep for a couple of hours. It wasn’t great, but it was just enough to take the edge off, so when the time came, I felt sort-of OK to head out for the event. The drive started to convince me this wasn’t the best move, but once I got to the event and sat down I figured I was going to make it. :)

Chris did two talks at the event.

IN/EXISTS bugs

Here’s a simple data set – I’m only interested in three of the columns in the work that follows, but it’s a data set that I use for a number of different models:

Index Usage – 4

Here’s a thought that came to me while I was writing up a note about identifying redundant indexes a few minutes ago. Sometimes you end up supporting applications with unexpected duplication of data and indexes and need to find ways to reduce overheads. Here’s some code modelling a scenario that I’ve seen more often than I like (actually, just once would be more often than I’d like):

Index Usage – 3

In my last note on index usage I introduced the idea of looking at v$segstat (or v$segment_statistics) and comparing the “logical reads” statistic with the “db block changes” statistic as an indicator of whether or not the index was used in execution plans. This week I’ll explain the idea and show you some results – with a little commentary – from a production system that was reported on the OTN database forum.