A SQL statement can be executed in many different ways, such as full table scans, index scans, nested loops, and hash joins. The query optimizer determines the most efficient way to execute a SQL statement after considering many factors related to the objects referenced and the conditions specified in the query. This determination is an important step in the processing of any SQL statement and can greatly affect execution time.
results let you determine whether the optimizer selects a particular execution plan, such as, nested loops join. It also helps you to understand the optimizer decisions, (more...)
I'm speaking next week at the UK Oracle User Group at the ICC in Birmingham. The topic will be one I've posted several times about which is Tuning, Refactoring and Instrumentation. Have a look at the agenda, and if you are in town, come along. You can click on the image to go to the conference site and check out the agenda.
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...)
Optimizer Hints like Index, Cardinality, Ordered ... are local settings to a SQL statement. Local means the context given is the context of the SQL statement, the scope is local. If you query a View you cannot use for example an Index hint because the table names and aliases are hidden behind the view. So normal hinting would not work without changing the view to add a hint.
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...)