Ad: The Method R Guide to MASTERING ORACLE TRACE DATA

The second edition of Cary Millsap‘s MASTERING ORACLE TRACE DATA (MOTD) is finally available. You can order it through amazon.com. I had the pleasure not only to review MOTD while Cary was working on it, but also to write a foreword that summarizes what I think about the book. So, if you are asking yourself […]

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Wrong Results Involving INDEX FULL SCAN (MIN/MAX) in 12.1.0.2

One of my customers that recently upgraded to 12c hit a bug (22913528) that I think is good to be aware of. Note that as the title of this post states, the problem only occur in 12.1.0.2. At least, I wasn’t able to reproduce it in any other version. To reproduce it you simply need […]

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Also Extensions Created Because of SQL Plan Directives Can Invalidate Packages – Take Two

In a previous post I described a situation where the creation of an extension, independently of whether it’s carried out manually by a person or automatically by the database engine, can lead to the invalidation of PL/SQL objects. In this second post on that subject, I describe, with the help of an example (I love […]

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Oracle Database In-Memory Demos

In the last 14 months I delivered a dozen of presentations covering the In-Memory Column Store. During many of them, I spent most of the time showing the audience several demos. The aim of this post is to share with you the scripts and a recording (MP4) of those demos. Warning about Demos The recordings […]

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Also Extensions Created Because of SQL Plan Directives Can Invalidate Packages

UPDATE 2015-12-18: As metioned by Bryn Llewellyn in this tweet, the invalidation I describe below is caused by bug 19450314. A patch for it is available here for several releases (e.g. it is available for 12.1.0.1.0, 12.1.0.2.1 or 12.1.0.2.13, but not for 12.1.0.2.0). I successfully tested it on 12.1.0.1.0. The fact that an extension explicitly […]

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Auto SGA Management Impacts the Default Value of DB_FILE_MULTIBLOCK_READ_COUNT

The database engine determines the maximum disk I/O size used during multiblock reads (for example, full table scans or index fast full scans) by multiplying the values of the db_block_size and db_file_multiblock_read_count initialization parameters. The db_file_multiblock_read_count initialization parameter can be set explicitly, or, as of version 10.2, it’s also possible to instruct the database engine […]

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Online Training Ad: Oracle Database 12c – New Performance Features

On 10 December 2015 I’ll give an online training entitled Oracle Database 12c – New Performance Features. This short post provides key information about it. Description With every new release of Oracle Database, a number of features aimed at improving performance are introduced. It goes without saying that 12.1 is no exception to the rule. […]

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Foreign Keys and Library Cache Locks

In this post I would like to describe a behavior of Oracle Database that, at least for me, isn’t obvious at all. Actually, it’s something that I can’t explain why it works in that way. Let’s start by setting the scene by describing the schema I’m using for the following tests. As you can see […]

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Bugs Related to SQL Plan Directives Pack and Unpack

SQL plan directives are a new concept introduced in version 12.1. Their purpose is to help the query optimizer cope with misestimates. To do so, they store in the data dictionary information about the predicates that cause misestimates. Simply put, the purpose of SQL plan directives is to instruct the database engine to either use […]

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Ad: Trivadis DK Opening Event

Trivadis, the company I work for, just opened a new branch in Denmark (the press release, in German, is available here). On the 14th of April (09:00-15:00) takes place, in the Oracle’s office in Ballerup, the opening event. Two colleagues of mine and I will be there to deliver the following presentations: Big Data versus […]

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