This whole thing about “not exists” subqueries can run and run. In the previous episode I walked through some ideas of how the following query might perform depending on the data, the indexes, and the transformation that the optimizer might apply:
from t1 w1
where not exists (
from t1 w2
where w2.x = w1.x
and w2.y <> w1.y
As another participant in the original OTN (more...)
This is the second part of a series of blogpost on Oracle database PGA usage. See the first part here. The first part described SGA and PGA usage, their distinction (SGA being static, PGA being variable), the problem (no limitation for PGA allocations outside of sort, hash and bitmap memory), a resolution for Oracle 12 (PGA_AGGREGATE_LIMIT), and some specifics about that (it doesn’t look like a very hard limit).
But this leaves out Oracle version (more...)
One of the new capabilities of Oracle SOA Suite 12c
is the ability to control the SOA infrastructure thread pools, except the resource pools for EDN and the adapters, with Oracle WebLogic Server work managers. Each partition will has its own work managers defined. This allows you to separate services in partitions and, to some extent, tune them separately based on for example specific SLA requirements.
Well, this blog posting is not about explaining the (more...)
This is THE
MySQL performance book. Period!
Every chapter is very well crafted, with a precise balance between theory and practice, and full of invaluable nuggets, sometimes transcending the MySQL arena and applicable to any database!
Such cases are Chapter 2-Benchmarking MySQL and Chapter 3-Profiling Server Performance, very solid foundations for the reading ahead.
All over the text, authors propose tools, examples of use and proven diagnostic techniques, that will greatly improve your performance firefighter skills and enhance your knowledge of MySQL internals. Nevertheless, what I liked the most from this book is taking into (more...)
En esta ocasión les voy a contar sobre un problema muy singular y la forma en que fue resuelto, estoy seguro que muchos usuarios de AIX 6.1, y quizás de otras plataformas, deben tener este problema y no lo han notado aún.
La historia se remonta a unos meses atrás, había concluido el upgrade de una base de datos desde Oracle 10.2.0.3
hacia Oracle 184.108.40.206.3
Tuning has always being good fun and something like a challenge for me.
From time to time we are being asked to find out why something did run slow while you are sleeping; answering this question is, in most cases, a challenge.
My batch did run slow last night, can you let us know why? Or why did this query run slow? Are questions we, as DBAs, have to answer from time to (more...)
The first product I ever created after leaving Oracle Corporation in 1999 was a 3-day course about optimizing Oracle performance. The experiences of teaching this course from 2000 through 2003 (heavily revising the material each time I taught it) added up to the knowledge that Jeff Holt and I needed (more...)
I regret not being able to write new things more often, but in fact it only means I am OK: very busy with work, doing private stuff (which is important since life is not all about working), enjoying the three young kids and trying to achieve some good results in track and field. And for that last goal, I can say I did. After a few months of struggling to find a tiny piece of shape comparable to last years shape, just in time I found it. I won the gold medal in the Dutch Championships 400 metres hurdles. OK, be (more...)
At my current client site, I use AIX on IBM PowerPC kit. There is a neat little systems monitoring tool called “nmon” on AIX, which I quite like. I noticed recently that it’s available on Linux now, so I installed it on my machine, which runs Fedora 12. (more...)
Recently, I wanted to work out the maximum value of a column on a partitioned table. The column I wanted the maximum value for, happened to be the (single and only) partition key column. The table in question was range partitioned on this single key column, into monthly partitions for (more...)
I've just discovered that my current contract, with a healthcare company in Hampshire, will not be extended beyond the end of the year. So, in the current economic climate, I've decided to start a blog in order to drum up more business.My primary skills are in troubleshooting and tuning Oracle systems, from entire databases to individual SQL queries.
If you have an application running on an Oracle database and you need someone to investigate an issue on that system, get in touch.
"My name is Peter Moore. I am a professionally qualified and highly experienced database administrator with extensive (more...)