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How to disable a SQL Plan Directive permanently
By Franck Pachot . In 12c you will see a lot of SQL Plan Directives. Some are useful to get better execution plans, but some will trigger too much Adaptive Dynamic Sampling and that can become a big overhead, especially in Standard Edition. Then you don’t want to drop them – or they will reappear. You can disable them, but…
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SAP HANA SQL scripting optimization: the CE Functions
In SAP HANA, you have two possibilities to create the Calculated Views: Using the graphical method Using the scripting method with CE functions In this blog, I will demonstrate that CE Functions can improve performances from a Calculated View. First, I will give you some general information regarding the CE Functions. After that, I will show you the two different…
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SQL Server 2016 CTP2 : first thoughts about tempdb database
In my first blog about SQL Server 2016, I noticed during the SQL Server installation process that we are able to configure the number of files for tempdb. This is surely a great improvement but at this point, you may think that the configuration of the tempdb database is finished but in fact you’re wrong. Let me say why. First…
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Convert a snapshot standby to a new database
By Franck Pachot . A snapshot standby database is a nice solution when you want a temporary copy of the primary where you can do whatever you want (test a bug fix for example) and then convert it back to physical standby. But you don’t want to stay in that state definitely because you will accumulate archived logs from the…
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SQL Server 2016 CTP2 is out!
As announced by Satya Nadella at the Microsoft Ignite keynote in Chicago, SQL Server 2016 CTP2 is finally out and it follows a previous private CTP. This CTP will provide some interesting features to evaluate as: Always Encrypted Stretch databases Operational analytics However, this CTP does not stop here and will incorporate a myriad of new features and many improvements,…
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12c Dynamic Sampling and Standard Edition
By Franck Pachot . 12c is coming with more dynamic sampling, now called dynamic statistics and using the new Adaptive Dynamic Sampling algorithm. The goal is to have better estimations and better estimations gives better execution plans. However, this new approach will increase parse time because dynamic sampling kicks in more often, reads more blocs, and run more queries. It’s…
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How to import SQL Plan Directives
By Franck Pachot . Today I’ve presented SQL Plan Directives at the SOUG Romandie event. I had a question about the import/export of directives by Data Pump. The idea is that a lot of testing has been done on QA in order to validate the upgrade to 12c. A few directives had bad consequences (see Ludovico Caldara blog post for…
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DBA_SQL_PLAN_DIRECTIVE.LAST_USED
By Franck Pachot . If you have read Matching SQL Plan Directives and queries using it then you know how to use the ‘+metrics’ format of dbms_xplan. 21:49:54 SQL> explain plan for select distinct * from DEMO_TABLE where a=0 and b=0 and c=0 and d=0; Explained. 21:50:01 SQL> select * from table(dbms_xplan.display(format=>’basic +rows +note +metrics’)); PLAN_TABLE_OUTPUT ———————————————————————————- Plan hash value:…
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What that in-memory term is about, and what not
Everybody is talking about in-memory databases these days. And everybody is talking about columnar store for sets of data because this can be a benefit for analytic queries. And a lot of people start mixing these terms not realizing that these topics are not exchangeable. Traditionally in-memory means: Not persistent, but fast. And this is what pure in-memory databases are:…
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Alfresco: video thumbnails and transformations
Alfresco support, by default, the preview in your browser of some video formats like mp4 but doesn’t support some others like mkv, avi or wmv. Even if Google Chrome can read mkv files for example, if you try to use the action “View in Browser” (this is not the same thing as the preview), Chrome will not try to play…
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Row Store vs Column Store in SAP HANA
The SAP HANA database allows you to create your tables in Row or Column Store mode. In this blog, I will demonstrate that each method has its advantages and disadvantages and should be used for specific cases. Thanks to two kind of tests, I will show you that the Row Store mode should be used for simple SELECT SQL queries,…
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List all RMAN backups that are needed to recover
By Franck Pachot . This blog post is something I had in draft and Laurent Schneider blog post reminds me to publish it. With the right RMAN configuration you should not have to managed backup files yourself. The RMAN catalog knows them and RMAN should be able to access them. If you want to keep a backup for a long…
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