Infrastructure at your Service

Category Archives: Application integration & Middleware

Stéphane Haby

SQL Server Tuning: Detect SPARSE columns candidate

By | Application integration & Middleware | 6 Comments

dbi services search and test all tools or functions possible to optimize or to win something to propose the best tuning possible in their client.
The property of Spare columns is not the most used in client environment that we have seen.
This article present a script to find the potential columns that can have the sparse property with the usage restrictions to make a space tuning in your database and especially for Data Warehouse (DWH).

The database example that we used, is AdventureWorksDW2008R2.

 
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Yann Neuhaus

How to retrieve previous table statistics using Oracle dbms_stats

By | Application integration & Middleware | 4 Comments

Sometimes, you need to modify the statistics of a table. There are various reasons: either for the performance analysis or because the execution plan changed. Oracle offers two methods: statistics restore or statistics export. Both are in the dbms_stats package. 1. Statistics restore This method uses the procedure dbms_stats.restore_%_stats, where % can be table, schema, database, and fixed_objects. This is an example for a restoration of a table with definite timestamp. The starting situation is:…

 
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Hervé Schweitzer

A SQL statement is slow and suddenly fast? Have a look at “Cardinality Feedback”!

By | Application integration & Middleware | 2 Comments

Discussing with some tuning gourous we were made aware about this feature. It is not so far from the adaptive cursor sharing perfectly described in  Chris’s blog : http://antognini.ch/papers/BindVariablePeeking_20090718.pdf

This feature, compares the real execution (number of returned/actual rows “A-rows”) with some expectations (number of expected rows “E-rows”) and chooses another plan for the next executions if the difference between the expectation and the actual result is too big. “Cardinality Feedback” is not well documented in the Oracle documentation.

 
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Grégory Steulet

Simulating and testing I/O performances with ORION

By | Application integration & Middleware | One Comment

Since Oracle 11.2, Oracle provides ORION in the RDBMS binaries (in ${ORACLE_HOME}/bin). ORION is an I/O calibration tool allowing to simulating and testing I/O performances an Oracle database would be confronted with.

 

ORION basically supports four kinds of database activities based on either small or large I/O. ORION can, as any respectable I/O simulation tool, generate an adapted workload using a given percentage of reads and write operations.

 
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Yann Neuhaus

Simulating database-like I/O activity with Flexible I/O

By | Application integration & Middleware | No Comments

You do not want to install or configure swingbench, load runner etc. – just to test the performance of your I/O system based on filesystems? Then Flexible I/O is the right tool for you. This post provides an overview. In order to simulate Oracle database I/O workload on filesystems, ORION cannot be used since it only uses raw or block devices (scratching the filesystem). To simulate Oracle database I/O behaviour on filesystems, we can use…

 
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