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How to Find the Optimal Configuration for Your Virtualized Environment
Thanks to the New York Oracle User Group for allowing me to present and to all who attended for their valuable questions and comments. The presentation showcases a framework for finding optimal server...
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Importance of Data Clustering when Deleting in Batches
The inspiration for this post comes from the OTN discussion “Bulk Deletes from a Large Table” where I volunteered the idea that we can improve the performance by taking into the account the...
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Detecting Connection Imbalance in Oracle RAC
For Oracle RAC configurations that rely on spreading the load equally among instances, ensuring that inbound connections are balanced is quite important. Since I was not able to find a suitable metric...
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Confidence of Cardinality Estimates Optimization Techniques – When to Use?
Presenting on professional conferences frequently brings out important points that were not highlighted well enough. RMOUG 2015 was no different. After I presented my techniques for performance tuning...
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RMOUG 2015
I am very excited to be selected to present at RMOUG 2015. I got two presentations – “Managing Statistics of Volatile Tables in Oracle” on Wednesday and “Working with Confidence: How Sure Is the Oracle...
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What to Do about Tools Hoarding Parallel Slaves in Oracle
Most GUI tools use cursors with relatively small fetch size (around 50) to retrieve data from Oracle. They open the cursor, fetch some data, show it and then wait on user input. All resources related...
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“Orphaned” LOB Segments
Recently, after doing reorganization in Oracle 11.2.0.2.0 DB, I came upon a LOB segment that does not link to a LOB. That is, there was an entry in USER_SEGMENTS and USER_OBJECTS, but there was no...
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A Patch for JUST_STATS Package
An alert user recently notified my about a problem with the JUST_STATS package. It appears that it does not work properly with PARTITIONs. So, click here to download the first patch. Please note that...
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When Oracle would Choose an Adaptive Execution Plan (part 1)
Understanding when a useful feature, such as Adaptive Execution Plans, would fire is of crucial importance for the stability of any DB system. There are a few documents explaining how this feature...
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An Oracle Distributed Query CBO Bug Finally Fixed (After 7 Years)
Optimizing distributed queries in Oracle is inherently more difficult. The CBO not only has to account for the additional resources related with distributed processing in Oracle, such as networking,...
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When Oracle would Choose an Adaptive Execution Plan – General Thoughts
Adaptive Execution Plans is one of the most existing new features in Oracle 12c. This post is not about how this feature works or its benefits, but rather about when Oracle would choose to use it. In...
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RMOUG 2014
I was very excited to present at RMOUG 2014 – my first time at that conference. Unfortunately, I got sick and I had to cancel. The name of the presentation was: Working with Confidence: How Sure Is the...
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More on Dynamic Sampling Level 11 (AUTO) in Oracle 12c
In a previous post I showed an example of how the new AUTO dynamic sampling level (11) consumed significant resources for a very simple SQL statement. Here, I’ll try to find your why. First surprise!...
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What is the Deal with AVG_LEAF_BLOCKS_PER_KEY (DBA_INDEXES) !?!
AVG_LEAF_BLOCKS_PER_KEY column in DBA_INDEXES should show the average number of leaf blocks in which each distinct value in the index appears. Common sense and Christian’s Antognini’s book...
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Dynamic sampling in Oracle 12c – it goes up to 11. Really!
For the first time in many years, Oracle introduced a new option for dynamic sampling, and a major one for that – http://docs.oracle.com/cd/E11882_01/server.112/e16638/stats.htm#PFGRF95292 . The new...
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The Cost of Adaptive Execution Plans in Oracle (a Small Study) Part 3
My previous two posts, The Cost of Adaptive Execution Plans in Oracle (a Small Study) Part 1 and The Cost of Adaptive Execution Plans in Oracle (a Small Study) Part 2, focused on estimating the impact...
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The Cost of Adaptive Execution Plans in Oracle (a Small Study) Part 2
In my previous post, I tried to find out the performance impact of adaptive execution plans (AEP). During the test, I used OPTIMIZER_ADAPTIVE_REPORTING_ONLY parameter to switch on and off adaptive...
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The Cost of Adaptive Execution Plans in Oracle (a Small Study)
Adaptive execution plans is a new Oracle 12c feature. I consider it one of the most important ones. Oracle 12c would pick the join method based on the actual number of rows retrieved during the first...
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New York Oracle User Group (NYOUG) Fall 2013 Conference
Thanks to all who attended my session at NYOUG. As usual, it was a great experience! Download the presentation here and the white paper here. You can also download the spec here and the body here of...
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NYOUG Fall General Meeting (2013)
I am excited to present at the NYOUG Fall General Meeting (2013). I’ll be speaking about volatile tables in Oracle. They are not common, yet they can wreak havoc on the database performance when...
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