Tag Archives: Oracle performance

Parallel query performance consistency

A collegue just asked me “didn’t you have a query to see what SQL has ran in parallel?” I’ve used this months ago and completely forgot, but this might come in handy again some day, so I’ll put this here. col … Continue reading

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Oracle performance mystery: wildly varying query response time

At this moment I’m working on a very weird performance issue on our Oracle Universal Content Management database. This is the query (actually with binds of course. Values for dReleaseState and dStatus are the same as far as I could … Continue reading

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Statistics history, revisited

Tuesday last week I did a presentation on the Planboard DBA Symposium in De Meern, the Netherlands, about SQL performance issues. The scope of my presentation was what to do when a SQL statement suddenly does not perform adequately. Often … Continue reading

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SQL*Net message from client on sqlplus?

Here is a very weird issue I encountered recently. I was working on a test to find out whether different values of parallel parameters would result in better performance for a data warehouse setup. I had noticed that several important SQL … Continue reading

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Planboard DBA Symposium: 17 juni 2014

Dutch-speaking readers of my blog might be interested to know I’ll be speaking at the 9th Planboard DBA Symposium at Oracle Nederland in De Meern. There will be (Dutch) sessions for DBAs and middleware specialists. I will do a session about first … Continue reading

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Useful stuff from event 10053 traces – part 2

I would like to reflect once more on the “dynamic sampling used for this statement” message. Suppose dynamic sampling really happened with reason, because statistics were old, missing or otherwise insufficient. Now what?   Dynamic sampling because of missing or old statistics … Continue reading

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Useful stuff from event 10053 traces – part 1

In theory you can use event 10053 traces to see what choices the optimizer has made, which is very interesting if your query didn’t perform as it was supposed to do. In practice event 10053 traces contain an overwhelming amount … Continue reading

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