design

Recently my friend Sabine Heimsath asked a few of us native English speakers what the opposite of “technical debt” was. My immediate reaction was to say:

I’d say (sarcastically) “proper development” or “decent designer” or even “what we did 25 bloody years ago when we were allowed to take pride in the software we created!”

But my next comment was less reactive and more considered. And that was to say that I did not like the phrase “Technical Debt”:

A debt is when you owe something to someone, to be paid back. You do not owe anything to someone when you build poor systems, you are actually creating a “technical burden” – something those in the future will need to live with and may eventually have to sort out. Those who created the bad app or design will probably not be the ones fixing it – as in paying the debt.

Some years ago I wrote an article for the UKOUG magazine called “Want a faster database – Take a drive on the M25”.  For those not familiar with the United Kingdom, the M25 is one of its busiest roads (M = “motorway”) and because it moves so much traffic, and runs so close to capacity, it has often been referred to as “the world’s largest car park”.  Many people have probably spent a good part of their lives on the M25   I used the M25 as a metaphor for how database professionals can focus on the wrong things when trying to solve a performance problem, such as:

“I’m stuck in traffic…perhaps a faster car will help”

ie, throwing CPU at a problem that is not CPU bound will not help things, or

“I’m stuck in traffic…it must be the width of the paint on the lane markings”

Way back in 2004 I was working at the UK side of the Human Genome project. We were creating a massive store of DNA sequences in an Oracle database (this was one of two world-wide available stores of this information, for free & open use by anyone {* see note!}). The database was, for back then, enormous at 5-6TB. And we knew it would approx double every 12 months (and it did, it was 28TB when I had to migrate it to Oracle 10 in 2006, over 40TB 6 months later and grew to half a petabyte before it was moved to another organisation). And were contemplating storing similar massive volumes in Oracle – Protein, RNA and other sequence stores, huge numbers of cytological images (sorry, microscope slides).

My good friend Toon Koppelaars created a cool and very interesting, learning video about how…

Quick, which database is the biggest space consumer on this system?

Database                  Total Size   Total Storage
-------------------- --------------- ---------------
SAD99PS                    635.53 GB         1.24 TB
ANGLL                        9.15 TB         18.3 TB
FRI_W1                       2.14 TB         4.29 TB
DEMO                         6.62 TB        13.24 TB
H111D16                      7.81 TB        15.63 TB
HAANT                         1.1 TB          2.2 TB
FSU                          7.41 TB        14.81 TB
BYNANK                       2.69 TB         5.38 TB
HDMI7                      237.68 GB       476.12 GB
SXXZPP                     598.49 GB         1.17 TB
TPAA                         1.71 TB         3.43 TB
MAISTERS                   823.96 GB         1.61 TB
p17gv_data01.dbf            800.0 GB         1.56 TB

It’s harder than it looks.

I started my Oracle working life as a builder – a Forms & Reports Builder (briefly on SQL*Forms V2.3 but thankfully within a month or two we moved up to SQL*Forms V3, SQL*reportwriter V1.1 and SQL*Menu 5 – who remembers SQL*Menu?). Why were we called Builders? I guess as you could get a long way with those tools by drawing screens, utilising the (pretty much new) RI in the underlying Oracle V7 to enforce simple business rules and adding very simple triggers – theoretically not writing much in the way of code. It was deemed to be more like constructing stuff out of bits I guess. But SQL*Forms V3 had PL/SQL V1 built in and on that project we used it a *lot*.

I’m now doing a second session at OUG Ireland 2015. {This is because one of the accepted speakers had to drop out – it sometimes happens that, despite your best intentions, you can’t make the conference and it is better to let them know as soon as you can, as they did}. This will be a talk called “Oracle Lego” and it is one I put together a couple of years ago when I decided to try and do more introductory talks – talks aimed at those who are not {yet} experts and who I think tend to get ignored by most conference and user group agenda. So it is aimed at those new to oracle or experts in other areas who have never really touched on the subject.

Last week I put up a post about how Oracle can filter out sections of a union view..

Within the comments I put up another example where the CBO did not filter out all but one of the Union views despite my replicating the exact WHERE clause of one of the unioned statements. Jonathan Lewis posted a followup to say “Oracle can be very touchy about how it plays this game” and made a prediction of how the CBO would handle a slightly different scenario.

This was the extra scenario and I include brief details on creating the unioned view too. NB all on Oracle 11.2.0.2. {non-Exadata }

My last post was on slow dictionary queries caused by having many, many thousands of extents in your database. This post is about a special case of this problem, which I encountered recently. It was on an Exadata box – Exadata is not particularly relevant to the issue, but I’m curious to see if mentioning Exadata will make this post more popular

I was querying the used and free space on a very small database on the client’s X2-2 1/4 rack Exadata machine. The query was really slow, taking about 30 seconds. This is a FAST box, what is going on?

I quickly realised that the problem was specific to one tablespace:

When preparing the material for my “Oracle Lego – an introduction to Database Design” presentation for the UKOUG last week, I was looking back at my notes from a course on the topic from “a few years back”. There were a few bits which made me smile.

Oracle’s [SQL] implementation conforms to ANSI standard, although referential integrity will not be enforced until version 7