Category Archives: Oracle performance tuning

Tracing Oracle background processes with Dtrace for Linux

I’ve been googling for articles on using Dtrace with Oracle databases. There isn’t all that much. I’ve found an article from Andrey Nikolaev on using Dtrace to investigate exclusive latches on Solaris. He uses this dtrace command to investigate the … Continue reading

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Trace column 1.3

trace_column.sql is a script that you can use to quickly trace (event 10046) a couple of sessions with the same properties. For example: suppose there are multiple sessions of a user called APP_USER, you can start the trace on all … Continue reading

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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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Function based indexes sans the NULLs

A collegue asked my help with a performance issue. He was trying to tune a query that ran on a 6 TB table. The query had to return rows for a couple of specific statusses and for that it should … 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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