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Index unique scan and the Clustering Factor: does it matter?
When the CBO evaluates the cost of using an index it uses the following formula: The third line of the above formula multiplies the index clustering factor by the effective table selectivity. This...
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Recycle bin: what’s going on?
Have you ever been confronted to such a kind of explain plan? Look carefully to the operation 4 Bizarre!!! From where does this index come from ? More bizarre is this: The Recycle bin is empty while...
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Interprétation d’un fichier TKPROF
J’ai été destinataire d’un fichier de trace TKPROF correspondant à une requête qui ne s’exécutait pas en un temps acceptable. Le but de cet article est de faire un résumé, étape par étape, de mes...
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2012 in review
Finally, 2012 came to its end. Unsurprisingly my blog has not been as active as I wished it to be. My busiest day was September the 18th in which I have published an article about interpreting TKRPOF...
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Oracle cached sequences
When dealing with Oracle sequences it is well know that cached sequences values are not lost following a tidy shutdown of a single database instance whereas a brut shutdown will generate a loss of...
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SQL PATCH and invisible index
I was playing with the demo presented in the oracle optimizer blog on how to use SQL path to inject a hint into a packaged application and then decided to extend it a little bit to see how this SQL...
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SQL Patch and SQL Plan Baseline how do they collaborate
In my continuing process of investigating SQL Patch and SQL Plan Baseline I wanted to know how these two technologies collaborate together. As I did in my preceding blog article I used the demo...
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ORA-02431: Cannot disable constraint
Recently a question came up on the otn forum which reminded me to write a small blog article that I will be referring to instead of creating a different test each time I see people asking how to...
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Sql Plan Mangement(SPM) and Adaptive Cursor Sharing(ACS) : My résumé
I read Dominic Brook’s interesting article about Adaptive Cursor Sharing and SQL Plan Baseline. I, then, have read the also interesting follow-up blog article written by one of those modest and smart...
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What can impeach Adaptive Cursor Sharing kicking off?
I ended my last post about the interaction between ACS and SPM by the following observation How could a creation of an extra index disturb the ACS behavior? Well, it seems that there is a different...
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Interpreting Execution Plan
I have been confronted to a performance issue with a query that started performing badly (6 sec. instead of the usual 2 sec. ) following a change request that introduces a new business requirement....
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SPM baseline selection: how it works?
In my last post about SQL Plan Management (SPM) I investigated the behavior of Adaptive Cursor Sharing (ACS) feature in the presence of SPM baselines. I will now start focusing my interests on the...
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Literal, bind variable and adaptive cursor sharing: simplify them please!!!
When you find yourself very often typing the same set of sql statements you will end up by writing a sql script in which will be collected those sql statements. As such, you will have avoided...
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Jonathan Lewis philosophies : french translation
Les lecteurs francophones peuvent trouver, ci-dessous, une traduction de presque toutes les philosophies de Jonathan Lewis. Philosophie 1 Il existe certains concepts Oracle très importants si bien...
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SQLTXPLAIN: Execution plan and operation order : Exec Ord column
I’ve recently decided to start exploring the Oracle SQLTXPLAIN tool developed by Carlos Sierra from Oracle support. Up to know I am still exploring the different possibilities that tool offers for...
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ORA-08102: index key not found: Part II
Last year I wrote a note about how I succeeded to overcome an index key not found error by moving the underlying table not without mentioning that an offline rebuild of the corrupted index reveals to...
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Different sql id, different force matching signature, different rows...
Very recently, two interesting blog articles, here and here, have been published to emphasize the possibility of having a same plan hash value for actually two different execution plans. Since then, I...
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Index Coalesce : sys_op_lbid
A recent question on the oracle French forum about rebuilding indexes remembered me to write a small note to show the existence of a more interesting option to use when maintaining an index but...
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Indexed virtual column and DML error logging : ORA-03113: end-of-file on...
This is a brief note to show you that when combining virtual column and DML error logging you might be in trouble as I have been. First the model create table t1(n1 number, dat1 timestamp(6)); alter...
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INDEX FULL SCAN , NLS_SORT and ORDER BY
If I was to ask you how an INDEX FULL SCAN is operated by the SQL engine you would certainly answer that it will go to the first leaf block of the index and walk down up to the last leaf block in the...
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