Interpreting Event trace file example — http: What is needed to diagnose a SQL Tuning issue? And each takes some time to collect. Along the way, we will also gain insight into how the Cost Based Optimizer CBO arrives at the cost for a query and, ultimately, how it arrives at the execution plan. We will compare both traces at some points, but mainly focus on how the costs were computed for the bad plan. These SQL text variations were made manually with an editor.
When time permits, I do volunteer to help on an analysis. Because the SQL is different each time, a hard parse is forced each execution. Oracle Performance — H. Oracle Support Case Studies are written by support engineers who work with customers on a daily basis. Still I think our eagerness to help blinds us a bit. The second trace file is not there because I did not force a hard parse on the second statement execution.
Trace helps to explain the similarities and differences.
Case Study: Analyzing Trace Files_Ryan_新浪博客
This script displays the trace file name. So this may not be accurate if the SQL has binds and bind peeking is enabled.
Every so often I see on a distribution list a posting that starts like this: Little experience with the subject matter Case Study Abstract Filss case study uses a tracefile from an actual service request to illustrate a methodology for analyzing trace files.
Here is file demo. No such file or directory -rw-r 1 oracle asmadmin Aug 7 Some experience with the subject matter Beginner: Again, there are two trace files.
So, if you get to read this, and you want to help yourself while using SQLT but feel intimidated by this little monster, please give it a try and contact me for assistance. Please note that event trace files were designed to assist Oracle developers and support personnel to diagnose optimizer problems and are subject to change with every new patchset or release.
To run tracethe user must be granted alter session. By continuing to use this website, you agree to their use. Notice that each time you call randtfi. About half the time is dedicated to short guided labs, while the other half uses presentations and demos.
Use and events for detail analysis of CBO decisions, changing the value of an optimizer parameter for a […]. I tried to create a small demostration for a better understanding of this event dump, following script creates a table with a primary key and unique key constraints and the CBO decides to use the unique key constraint over primary key; Code listing These SQL text variations were made manually with an editor.
Fill in your details below or click an icon to log in: You are commenting using your Twitter account. The good plan is basically a studh version of the bad plan one in which no indexes were considered.
Written by Carlos Sierra September 2, at 5: Our Support Case Studies are created for the purpose of sharing information and for transferring knowledge related to a complex event, process, procedure, or to a series of events.
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Click here to read the entire case study. The Case study program is no longer in existence. Expert About Oracle Support Case Studies Oracle Support Case Studies are created for the purpose of sharing information and for transferring knowledge related to a complex event, process, procedure, or to a series of related events.
I always wondered how and why Oracle optimizer decides to caxe one execution plan to other. The first trace file viles a continuation message on to the second:.
Written by Carlos Sierra May 8, at 5: Atudy workshop is packed with lots of content. It was a real challenge packaging so much info in only two days, but I am very pleased with the result.
Scripts for trace 10053
Optimizer debug trace event, trace file The trace file we produce has lots of information as expected; all session optimizer parameter values and every table, index and possible access path statistics etc. The intentions are always good, but the process is painful and time consuming.
The row length would have to come from the catalog.